I'm not aware of a red light district, at least not one near tourist areas.  But if you Google for BA and "travesti", you should be able to find some providers. English is likely to be your problem, but many of the sites say whether or not the girl speaks English, which you'll quickly find out is accurate or not. Incall rates for Eros type providers were able 100 pesos I as recall. Very cheap by US standards.

Its been awhile since I was there. Use the search button I think this is second time i've written about this?

At night, the red light pickup area is in the park by  Av del Libertador. I think around Av Infanta Isabel near the rose park "Rosedal". There are gg there also I recall. The night club Crobar is right near there. If you are not too shy just get in a cab and tell them you want "travetis" etc. I think its common enough that they won't be too surprised. I didn't avail myself of this method, but did go for a joyride with non-hobbying friends to see the "hookers". When the cabbie said those are dudes my friend was surprised and didn't believe until they displayed their cocks. Although I wanted to jump out and join the party I restrained myself. Ha. Some people opt to get handies or bjs right there on park premises, though I wouldn't recommend it.
The regular brothels may be an option. They are more like strip clubs with dine-in and take-out. If you tell a girl there that you are looking for shemale action they should be able to help out. But, I defy you not to partake of GG talent once you step into one of those places. It was more than I could pass up. I think I went to "Blacks".

I hooked up 2 times with t-girls from distinas. My spanish isnt the best, so phone conversation was difficult for me. But I managed to see two girls with apartments near Galleria Pacifico mall. The "apartments" were a little sketchy. One was a pay by hour kind of thing. But I'm still here.

There is also a daytime pick up joint for GG at a coffee shop directly across from the mall. Just walk around the perimeter of mall and you will find it. When you get to the coffee shop with 20 women who make eye contact with you, you will know you are there.

Other advise...
Depending on the length of stay, rent an apartment. You can get a nice modern condo with privacy for less than hotel cost. That privacy also equals risk in the event anything go wrong. Just use your (big) brain and the room's safe.

Beware cab drivers. Other than driving like maniacs, they are a surly bunch. Be sure to have low denomination bills or you will incur wrath. They have serious issues with breaking a $20? Something to do with the currency shortage. If they do break a big bill for you they will try to pass of counterfeit bills on you FOR SURE. Always check the bills in the car light and return the fakes. When you get fakes, just use them the next time in a cab and walk away They love nothing more than a drunk fare after dark. You'll find yourself with a pocket of monopoly money the next morning.
Nightclub bars use an annoying 2 person system where you buy tickets from one person and use them with a bartender. For some reason the local version of redbull "speed" is the cheapest mixer. A soda or cranberry will cost more. Must be subsidized by the state to contribute to tourist drunkenness to ease the flow of counterfeit currency. Whatever the case its usefull for staying out late since locals don't hit clubs before 1-2 am. If clubs are your thing its a great place to be, can get bottle service for like 50 usd. hot chicks, fun parties.
Um what else? Eat lots of steak, Italian food, empenandas.