Depends on what you like. I stuck mostly to the dives, places like Pattie's. It's a complete shit hole, but has the cheapest drinks in Old Town, and a pretty diverse/fun crowd. You will be hard pressed to find a place that isn't rocking and rolling this weekend. The high end places that aren't clubs like American Junkie will have tons of hot chicks, but drinks are expensive.There is a tiny (understatement) honky tonk bar called the Rusty Spur Saloon I highly recommend you check out for a drink. It has lots of character. The Lodge is worth a stop too.
On Mill Ave, I recommend a drink at Rula Bula Irish Pub. It also has character, compared to the rest of the Mill bars that change names, ownership and themes every other year. If you can, eat at Monti's on Mill. It is the oldest building in Tempe, serves the best steaks for a decent price, and is closing for good in a few weeks, so it's now or never.