Many people on here don't like dog parks, so be prepared for lots of negative comments. Kimber, on the other hand, grew up at the dog park and I don't know how we'd have gotten through her first few years without it.
First, check to see if there are posted rules. Some dog parks do not allow intact males.
Next, I'd go at a non-busy time, like a weekday morning. It's best to try going when there are just a few dogs. Chat with the owners and find out when the quiet times are, who are the good/bad owners, etc. In the better dog parks, there are "regulars" who encourage good behaviors among other dogs and dog owners.
At the park: pay close attention to your dog at all times. DO NOT sit on a bench or start playing with your phone. Follow Jesse around- not to get in the way, but so you can step in if things go south. If he plays nicely, that's great! If he seems to have fun with specific dogs, ask the owners when they normally visit the park. Informal play dates at the park are fun.
If he starts to hump another dog, step in to break it up. If he can't stop humping, leash him up and go home. That's not a death knell for dog parks; it's just a way to teach Jesse that humping=fun ends, and for you to keep from going crazy because he.won't.stop.humping.
If as an intact male he becomes the target, step in. Ask the other dog owner's to redirect his dog. If that doesn't happen, leave and go back another time.
While he plays, have him "come" to you often. Just give him praise and send him back out to play. Too many new owners only call the dog when it's time to leave and then get upset when the dog makes the connection "come" means fun ends and stop responding.
Dog parks can be wonderful opportunities for dogs. You'll hear horror stories but in my experience, the benefits outweigh the small risk.