Things have not changed in 10 years. Most SG's will ask for $20 half nude but others will go for 100 pesos (9.50 US) full nude.  You just have to learn to bargain.  Don't ever ask THEM how much.  You ask them if 100 pesos is OK, then wait and watch for the reaction.

Room rates average $4 ranging from $3 to $5.  "Normal" session is 15 minutes but you do not have to be "normal" and can bargain more time.

I don't bargain for a half hour on the street but wait till I check them out for 15 min. in the room.. Most will accept double pay for twice the play.

Quanto questa por media hora?  (How much for half hour?)  I would say after 15 min.  100 pesos mas por quince minutos mas?
Your milage may vary.

Young ones (over 18) can be found on Constituion or the alley.  Just walk and look.

Don't assume anything with any chica in the Zone but especially  the SG's you have to spell it out all down stairs.
If you're upstairs and want her naked, give you a BJ (covered or bare), anything else you may want (facial, anal..etc.) it probably ain't going to happen since ALL has to be negotiated up front.
I've only seen one SG and my friend set it all up for me but from what's been said, most street girls won't take their tops off, will roll up their panty hose on one leg to expose her pussy. You enter, you get off and usually no place to wash up.
You don't pass GO and don't collect $200 either.
Basic sex at it's minimum in service time and most times quality.
There are many guys that are TJ vets with the SG's but it's from a lot of experience.  

If you want a better session that's worth the $ per minute, look at the club girls since you don't speak Spanish.

You might try a few guys on the street to interpret like Texas Mike or Franco but these guys expect a tip or propina when they help you negotiate. Or you can go to a language translation site, print up all you want and you can point to the print up, it's cheesy
HA,  
but it works.