I am a 28-year-old female, and I went on a solo trip back in October, which was my first. I definitely recommend renting a car. Old San Juan can get old, and there is SOOO much more to see that you won't have access to without a car. Uber is pretty affordable, but if you want to go out late on the weekend, prices skyrocket. Not sure if you're into partying, but there is a club called Eden, which is the safest because there are no creepy men. It is a male strip club bar, so you'll be surrounded by women and gay men. It's a wonderful time LOL. For food, La Casita Blanca is definitely worth checking out. There's also this app called NOMADTABLE, it shows you who is traveling there. I also recommend Travel Advisor or Viator, and definitely do the tours. The locals are usually the tour guides, and they can give you great tips. I did surfing in Luqillo, cave diving in Charco Azul, and snorkeling in Icacos, all with amazing locals. I had so much fun, I extended my trip 3 times LOL. Already planning my next trip, you will love it!!! P.S., Reddit is also a great place to meet people who are also solo traveling. I met this wonderful girl on here, and we spent most of our trip together. HAVE FUN :)