Some buddies and I are going down to the Keys in July. None of us have been. We’re mainly just going down to sit on the beach and fish. Anything we should take time to do and things/places to avoid? We got the Airbnb in Vaca Key confirmed today.
Having spent plenty of time in Ft Myers, I am up to date with FL carry regulations and all that, but not sure how carrying while off shore fishing would work.

Get some decent snorkle gear and check out Sombereo Reef and Coffins Patch.

If you're going on a charter they may have other sites they prefer.

There aren't many beaches in the keys. Some resorts have manmade beaches.

For me is all centered around fishing, lobstering and diving. Are you and your friends scuba certified?

Most carter boats won't let you bring a firearm onboard if asked but they are not searching your backpack either. If you must carry on a boat put it in a dry bag in your backpack.

None of us are certified.
We are setting aside a day or two to charter a boat. None of us have saltwater fished before though.

There is a head boat that runs out of Marathon called the Marathon Lady. She's 73 foot and when I rode her I caught lots of yellowtail snapper and grouper.  It's a great boat for beginners since they provide you everything you need and it doesn't cost a fortune like a charter.

Feed the tarpons  at Robbie’s.

Not a bad choice and a fair price to get out on the reefs. the boat is long time family owned and some of the crew/mates are generally family or close friends.  They will definitely make effort to move to get on fish if a spot is slow. We always try to hit the night trip when we are down. Lots of great places to get food too. The bridges are always an option to fish from. Definitely suggest seeing Sombrero reef. Key west is worth a day trip to eat/drink and meander around, catching the sunset at Mallory square. Maybe rent a boat for a day or two and see what kind of fish you can pull off the patch reefs, or sight fish the weed patches or birds feeding. Charters are always an option but they are easily north of 1k but they arent as painful if you have 3 or more to put in on the trip to get out and maybe catch a once in a lifetime fish.

Good to know, I appreciate it.
What about spots to eat? We are planning on making our own meals at the condo for at least half the meals, but I’d love to hit up a couple good Cuban places.

Robbie’s to feed the tarpon
Key fisheries on marathon for food

Grab some dinner at The Green Turtle Inn in Islamorada.

Cuban Coffee Queen. They had a few locations in Key West last time I was there. It's been a while though.

La Nina on Marathon or Sunrise Cafe in Tavernier are the only two Cuban places I would recommend. They are not very formal places, so check their operating hours before driving over.

I try and stay out of Key West but there are a few good Cuban places there as well such as El Siboney.  

If you fly into Miami, try and stop by Versailles. It's pretty close to the Airport. Yeah, it's turned into a tourist trap, but it is still pretty good and you will likely enjoy the experience.