Definitely stay in BA, IMHO. www.hostelbookers.com for reasonable single rooms. Plus at those sorts of places there is more mingling with other guests and you will get ideas things to do. And directions. Might even find some nice friends? You clearly have a couple that need replaced.

Housing solved, just wander. Classiest shopping ever, if that interests you. Elegance on a par with Paris. Buses/subways work well to move your body about.

If you possibly can, find a local tango performance. Not the touristy ones. Incredibly moving.

Buy cds or tapes of local music to bring back.

Well, yes, museums and history. Maybe even buy an english guide book?

Expand your Spanish vocabulary.

Food - even the local McDonald's is different that the US versions, but any of the beef places are grand. The menus are a hoot, starting with picures of actual beef cows on the outside and progressing on inside to where parts come from on the cows, to pictures of the raw meat on platters, before finally showing actual cooked stuff. (Oh - hope you aren't a vegetarian - apologies if you are.)

I travel by myself often. It works quite well. I spent 3 weeks in BA many years ago for a work project. Fell in love with the place, the people, the music, etc. Give it a chance.

And the ultimate revenge on the former friends of yours - have a great time!!

Romelle

But count your change. Smoothest short changers I ever encountered were at the train ticket office in BA. Got me twice, and I was a math major.