I went to school in Jan Jose for a few months. Nice place, but it can be very dangerous. I would advise your wife against wearing any sort of earrings that hang down...studs are fine, but hoops or hanging earrings are liable to be snatched right off the ear (and I saw that happen twice!)
Particularly with your wife, be careful with taxi drivers. A friend of mine studying with me was coming home late at night was was nearly raped by a taxi driver after he drove her to a remote location and stopped. She managed to stab him and run away, but it was a hell of a scare. They will overcharge gringos, so fluent spanish and a little wheeling and dealing should set them straight if possible.
Be VERY careful of the water. Drink coke only out of bottles, ESPECIALLY at small mom and pop restraunts. At malls, where there are mcdonalds, taco bell, stuff like that, fountain drinks are usually OK, but be wary.
Contray to what someone said earlier, there is net connection there. There are many net cafes, especially in the bigger cities.
Definitely try and blend in with the locals, dont wear overly "american" clothes or have a radical haircut.