GFS has an awesome restaurant w/ lots of variety, it's right on the beach, the rooms are very clean, and the staff are helpful and fun to hang out with.
Playa Gigante just edges out Ometepe for the title of my favorite spot in Nica (haven't been to Playa Popoyo, though -- I hear it's just as good, if not better). No crowds, totally relaxed, *very* little development, but several good restaurants and some great people.
If you want a good beach that isn't overrun with Americans, skip San Juan Del Sur and come here. The beach in SJDS isn't half as beautiful, the entire horizon is lined with boats, you have to travel a while to get to the good surf spots, and everything is *much* more expensive and crowded.More