I've stayed at Mare for 5 different weeks this year, staying a different rooms (#33, 32, 27, 22, 21). It's my go to place in San Juan. Having traveled for 30 years on business, Mare meets and exceeds my expectations. For the rate, you cannot find a better deal. The hotel is clean, modern furnishings and has all you need if looking for a basic service hotel and not wanting to pay resort fees and other hidden costs.
It is located on great, quiet residential street. You can feel like a local. Once you find your morning coffee and breakfast hangout (Regina across the street), you can head out to the beach (down the street) or venture further to Condado (walking 10 to 15 mins). I rent a car while in Puerto Rico and have no trouble finding street parking (avoid exorbitant hotel overnight parking fees). If you are expecting a pool boy or room service, this is not your place.