I'm about 40-50 miles south of Ft. lauderdale. If you want to be near the beaches or action, you will need to stay east of I-95, and there are lots of hotels to choose from. Priceline, etc work well for me, since I dont have personal experience with any hotels there.
Las Olas is a decent nighttime area. Its basically downtown riverfront. Not exactly walking distance to beaches, but lots of clubs and restaurants. Rental car is the best way to get around.