Make sure you do all of your souvenir and clothes shopping in other parts of town before coming to Puerta de Tierra. If you are buying groceries, your options are slim as well. Try to do grocery shopping in other parts of town if you want any food beyond snacks. There are two options near the hotel for snacks, toiletries, and practicalities. In the Hilton, there is Caribe Sundries, which by far has the best selection of toiletries and painkillers. There is also another convenience store called Mini Mercado, which is open 24 hours and has a decent selection of food and exactly one variety of shampoo and conditioner each, for those of you who can't make it to the Hilton. It is easy to find at night; the windows are lined with green neon lights. When buying in Puerta de Tierra, or anywhere in San Juan, look for locally made snacks and products to save a little money.
If you are desperate to shop and have a little bit of extra money, there are stores in the Hilton, although they are expensive and mainly sell jewelry and designer clothes.