Which would you recommend

Those are three nice choices to have. I know many people love Guanj., but I do not know it well. I do know Oax and it certainly fits all your desires. It is one of the great cities of Mexico & and there and so many things to do in the general vicinity.

I second previous poster's vote for Oaxaca, having spent two weeks studying Spanish there a couple years ago. I was at Insituto Cultural de Oaxaca and loved it. Also had a really homestay. LOTS to do in and around Oaxaca. I love Guanajuato too - and one thing that might be good for a younger person like yourself is that it's a University town . .. . it's a beautiful city, but perhaps not as much to do in the surrounding area as there is in and around Oaxaca. ...

worterB a frequent poster on this board has a language school in or near Guadalajara, he is his website...Guadalajara is about 5 hours by bus to Puerto Vallarta for the weekends or to San Miguel Allende or GTO the other way...suerte

Here's my opinion; all three cities have a history, Guanajuato will most likely provide the most fun for someone your age, all three have plenty of 'sights' and good options for weekend excursions.

Buen viaje!

Thanks for all the advice everyone. I was leaning towards oaxaca, but i still have lots of research to do. Now i can narrow down just a bit more with your help. Again thanks.

Aloysius, have you spent much time in guanajuato? If so maybe i could ask you a few q's about it.

Mexico City or San Miguel de Allende, are the first two places I´ll suggest you seriously consider.

You can't go wrong with Guanajuato or Oaxaca. Both are beautiful university towns with lively vibe. Both have good daytrip options. And both have lots of language school options. Oaxaca has better food though.

thanks for the added info, i am now leaning towards oaxaca.