I don't know what your agenda is for your trip, but I would wholeheartedly recommend spending some time in Old San Juan. The Hassy would be fine for shooting around the neighborhood, with the caveat that the streets are quite narrow and you will want to have at least the 50mm, if not a super-wide. The sun is quite bright and intense - I would advise leaving the Tmax 400 at home unless you want to do some night shooting. I posted a few of my recent shots from old San Juan here in the APUG gallery (and more on my blog) - they were shot with Kodak Ektar 100 (and an accidental roll of Portra 400 - this is how I know it's too fast - I was getting f16 @ 1/500th or 1/1000th of a second, making it hard to control depth of field. The San Cristobal and El Morro forts are great subjects, but I don't think they allow tripods. Check on the Park Service website (the forts are National Parks) to verify this.

While San Juan is generally as safe as any other big city, do be careful. The Hassy could make you a target for thieves. Especially if you are going to shoot at night, have someone to look out for you while you have your head buried in the waist-level finder.