Okay Fresno is my hometown (lived in the No, as we call it, from age 6 to age 18) so I have a unique, home-grown perspective. First off, it's really NOT a tourist town, it's about two hours from Yosemite, two hours from Sequoia and Kings Canyon, three hours from the Bay Area, four hours from LA. Not much to see actually IN Fresno. But if you happen to end up here, here's some things to do:
Tower District is the closest thing Fresno has to a nightlife area. It's located along Olive east of Palm Avenue for about three our four blocks. There's a couple of cool bars and nightclubs, restaurants, etc. The most popular bar down there is Livingstons. There is also some nightlife in North Fresno, like BeBe's on Shaw and Marks or a couple of bars in the Fig Garden Village shopping center, but if you're an out of towner, Tower is your best bet.
Fresno has great restaurants, but most of them are chains, like Famous Daves or Hooters or Outback Steakhouse. If you want good LOCAL cuisine, you gotta go to the bad parts of town. Tacos Tijuana is really good Mexican food and is open really really late, over on Ventura and Eighth, not far from the Juvenile Hall and the Fairgrounds. Another popular local spot is (or used to be) Chris' Meat Market (AKA April Meat Market) located on Kern and E, right where downtown borders the "West Side" neighborhood. It used to always be packed on the weekends, and looked like a car show out front, but the Fresno PD has put the clamps on that. The carne asada is still decent though. A local chain called Bobby Salazars is also very good, and they have several locations throughout the city, including one in the Tower District.
If you're in town for a show at Save Mart Center or an event involving the University, and are staying near the campus, there are always student parties going on in the apartments alongside Bulldog Stadium...just go in, find music and crash the party if you want! Most of the time, especially if you bring your own alcohol (or more importantly bring alcohol to share), you can party with the students. Be advised though, Fresno PD LOVES to crash parties. It's their favorite thing to do.
Finally, be advised that Fresno may not have the repuation of an LA or an Oakland but has some areas of town that are just as bad as any in those cities. The Tower District, for instance, is a small pocket in the middle of one of the poorest neighborhoods in the United States and the crime is bad in any direction if you stray too far. Essentially, if you're not from the area, try to stay north of Shaw Avenue (unless you go to the Tower to party) and lock your car up tight and take all your valuables out of it! And Fresno is NOT the place to try to drive after you've had a couple. The Police set up DUI checkpoints all over the city and they WILL impound your car and send you to the county jail which is not a fun place to be.