We live in that area and have stayed at several resorts over the years.
The Don Cesar is amazing but you're looking at about $300/night. We've stayed there a couple of times but only for special occasions. The "main" thing to do is the beach. The resort is gorgeous, though, and fun to just walk around. They have a great pool bar and if you want 5-star dining you cannot go wrong with the Maritana Grille!
The Tradewinds and Tradewinds Sandpiper are fantastic! Sometimes you can get deals for about $100/night at the Sandpiper. They have really cool stuff to do, including paddleboats and a giant slide. The beach is right there and beautiful, and the pools are really nice. Lots of good restaurants, too.
We stayed at the Sirata in 2008. It was wonderful - full kitchen, huge bathroom, gorgeous view. Lovely beach and nice pools. We got it through Priceline and paid $55 and the walk-up rate was about $55, too.
The Grand Plaza was recently re-done and is very nice. The restaurant on top is very good.
The entire area is gorgeous and you'll have a great time!