First make sure elevator requires a key card to access your floor. Many but not all do.

Tell her to dress appropriately which she probably does already and walk into the elevator towards the center with a group of other hotel guests. Once inside, ask her to politely ask another guest to enter the floor number for her. Many guest will do it without thinking twice about it.

You only need to swipe a card once to activate the control panel, then you can enter as many floors as you like unless you are a Mr. big shot and have a specially coded card for your floor.

Remember hotels don't really want to piss of guests unnecessarily and make things inconvenient for them.

but I have encountered this in the US, Canada, Panama, Costa Rica, Panama, The Bahamas, and Costa Rica, all within the last year.

Yeah it is a pain in the ass, personally I don't mind who sees me going upstairs with a beautiful lady, but the only practical advice I can give the OP is to get two room keys, meet your your young lady downstars, slip her one of the keys and then head upstairs separately.

Personally, I'd flaunt her (assuming she's hot of course) in front of my buds, "I'm getting some of this, and you're not, nya nya nya" but I can be rather juvenile at times. lol

It's a fucking pain in the ass, and I see it more and more nowadays.

I don't want to name specific hotels for obvious reasons but with the advent of technology and multimillion dollar hotel renovations, the idea of swiping a key card to use an elevator is becoming quite popular as it adds security and eliminates the extra security guard hanging around the elevator late night.

Pretty much all the major hotel casinos in Vegas require a key card to use the elevator or you must show a security guard at the elevator your room key. I had to use a key card at a mid-scale hotel in the Midwest just last week to use the elevator.

Depending upon whether she is coming over to your room, or vice versa.

Regarding the former, I assume you are having a convention of some kind, so it's  big hotel with function rooms, etc.  Have her meet you on one floor with the function rooms where there won't be any people around at that time.  Always ask for two keys, and you can give one to her, then head up and have her head up a few minutes later.

If the hotel does't have such facilities, then use a store or coffee shop within walking distance for this purpose.

If you are coming to see her, just use the converse procedure where she gets two keys and meets you.  She might also find a place somewhere in the lobby where she can leave an envelope with a key in it beforehand and direct you to where it is so she never has to come downstairs.  For example, she could place it in a magazine and leave the magazine on one of the end tables in the lobby.   A phone book at a pay phone would also work.  

Another way is to have her come down the elevator, but never get off same.  She describes what she is wearing (and you likewise) and when you see a car come down with her on it, you just hop on and both ride back up.

Hey - I am a first timer and want to call a lady over to my room.  I am sure you need a room key to access the elevator.  If I have colleagues walking around the hotel and don't want to be seem meeting a lady in the lobby - how do I avoid?

Where are you that you need a room key to use the elevator?  I think I've been in at least 1000 hotels in over 12 countries and never needed a room key to use the elevator.  Not saying there isn't one out there but...

I've been to several hotels that need a room key to use the elevator and usually my client just meets me in the lobby.
The hotels that require that are usually upscale hotels.

Personally, I would never leave a room key somewhere...   I think the coffee shop handoff is easy enough.  Agree key card access is a PITA.  
Hey, guys, stratigy for least conspicious room choice?  Maybe a different floor?!

As MrFisher said... Just exchange info on what each of you is wearing, have her wait at the elevator bank, ride down to get her and when you recognize each other, she just jumps in the elevator with you.  If people are around and extra discretion is needed, the two of you can pretend not to know each other and your reason for not getting off at the lobby with everyone else is a muttered "Oh damn, forgot my brief case/cell phone/etc."  You both ride silently up to your floor and she follows you off but heads in the opposite direction until the elevator doors close and the two of you are alone on the floor.

These things are so easy to navigate....

Yet again we agree. Few things bring such pleasure and pride than walking around with a gorgeous lady on your arm.

Especially when you KNOW in about 10 minutes she's gonna be nekkid in YOUR room! lol!

Look. I'm not married. Most people know what I do because I don't give a fuck what they think.

I have no problem, what-so-fucking-ever, taking the elevator down, seeing the lady du jour, grab her hand, and take her back up before the doors close.

I realize there's cameras everywhere. I don't give a fuck.

I give you your donation behind closed doors, and the only thing I can think of that might raise a flag is if we start to strip in the elevator and all the way to the room.

Don't get me wrong. I've grabbed and groped some of them on the way back up, and it was reciprocated, so I know it's cool.  

Last weekend I left a key with the front desk for my friend. It was easy.

Last fall I had a date with a travelling gal who stayed at a Downtown hotel that had elevator keys.  Once I got there she came down and met me next door where we shared a Starbucks, got the key from her, and followed her back a few minutes later.  Rather painless (although she kept apologizing for the inconvenience) and a tad more erotic, as I saw her in her jeans and just thought to myself what a great time was coming.  The few minutes delay gave her some time to prep for my arrival..and the rest was just a blur from there.

... best you could do is maybe tell her let you know exactly when she's about to enter the lobby and depending on how close you are to the elevator tell her you'll meet her in the elevator on the 1st floor and maybe the shirt you're wearing or something.

Thanks to fire regulations, once you are in the stairwell you generally have access to any floor.  Enter the elevator with other people in the lobby, ride to wherever the elevator goes, and then take the stairwell down to the appropriate floor.  Many times, as others have said, you only need the key card to activate the panel.  Once someone uses the card, you can push any button.  Sometimes, the card activates buttons for the appropriate floor and all floors lower.  You can test all this stuff ahead of time and tell her what she can do.

Honestly, most women have dealt with this before and handle it fine.  A beautiful lady can flash a smile and pretty much get whatever she wants if she's smart.

Or just quite worrying and meet her in the lobby.  Discretely go to your room.  Most people are not going to suspect anything.  And those that do, probably do only because they know from personal experience how these things work.