Yes, it will be hot. Keep hydrated, a lot of sunscreen and hats and you should be ok. Stick to the US National Parks that include both huge Spanish Forts that are walkable from the 1-4 piers; try walking west to Paseo la Princesa (where there is a playground), through the San Juan Gate and stick the left through the Save a Gato sanctuary and end at San Felipe del Morro. After El Morro grab a quick snack and walk to San Cristobal Fort and then around the city. This route has more shade and is less uphill (steep climb) than going through the city streets. Lots of areas for pictures, cannons and history at the forts. There are sorbet carts throughout the city with flavors like coconut, passion fruity and Caribbean cherry, they are really tasty and cheap. You can use google maps to trace your walk. Have fun!
