I'm looking to take a long weekend trip with the girlfriend to Puerto Rico in August (I know, it will be hot). We are two 30 year old who like the beach by day, but like to go out at night. Can anyone recommend some hotels that are on the beach and are relatively close to Old San Juan. Does not have to be walkable, but would like to check out the town one day. Or, if others recommend staying in the Condado area, please let me know about places you recommend there.

I think you'd like the Isla Verde area. It has the best beaches in the San Juan area and good nightlife. It's about a 15 minute taxi ride to Old San Juan (or around a 30 minute bus ride - which is only 25 cents).

There are a number of hotels that are on the beach - the Wyndham El San Juan (not to be confused with the Wyndham Old San Juan), the Ritz Carlton and the Intercontinental. There also are the San Juan Towers (which are time-shares/condos) and the Water Club (which is a boutique hotel).

You don't say what class of accomodation you're looking for but the Wyndham El San Juan is on a good stretch of beach, has beautiful grounds and pool area, several very good restaurants and excellent nightlife (which includes a grand lobby bar, a cigar bar, lounge with live music and dancing, a disco, and a casino.

It is right next to the Intercontinental and down the street from the Ritz Carlton. It is expensive but you can usually get a decent rate in the summer months. For example, they currently have some webrates for $153 per night.
Condado is somewhat closer to Old San Juan (although not walking distance). The only hotel I would recommend in that area is the Marriott.

We stayed at the San Juan Towers, also called he ESJ towers and I think that would be a good choice for a w.e. for you two. It is in Isla Verde, on the beach and close to Old San Juan.

Isla Verde or Puerta de tierra area would probably meet your needs. The El San Juan Hotel , Intercontinental, or Ritz are all good hotels in Isla Verde, however you will need to take a cab into Old San Juan ($20) to enjoy the great nightlife and restaurants there. The Caribe Hilton (Pta. tierra) is also nice and is closer and at the doorstep of Old San Juan. Just avoid Condado, sort of seedy and past its prime. I use to go there in my youth and am sad to see how it has gone downhill.

tom42, I noticed in your post, that you could only recommend the Marriot in the Condado area.. we are doing a post cruise stay at the Wyndham Condado Plaza. Do you have any info on that location, how far to walk to Old San Juan? Any info would be appreciated.

havi2000, Stayed at the Condado Plaza about three years ago. It is located just inside the entrance to Condado area. You can walk across a small bridge to Puerta de tierra where the Caribe Hilton is located. However you still will need to take a cab or bus to old san Juan. The CP was recently renovated and has a very lively Casino, however the beach isn't anything special.
If your looking for proximity to Old San Juan and lively night activities the CP will do just fine, however, if you are all about the beach I would choose a hotel in Isla Verde.