Honestly I wouldn't be overly worried. UO and Seaworld have both been open for over a month now and no outbreaks have been traced back to theme parks. The major problem areas appear to be bars, nightclubs, parties, etc. Anywhere that you have a large group of people crammed in a tight indoor space not practicing social distancing or wearing masks. That's why you've seen big outbreaks in the Miami/Dade area, for example. The theme parks have done a great job of mitigating a lot of the risks, putting some great practices in place, etc. Beyond that, it's just a matter of being smart. Wear a mask, distance yourself, etc. If you see a clump of people that looks iffy, avoid it. If you go into a restaurant that doesn't look properly distanced, try somewhere else. Personally I think a lot of the risk can be avoided just by being smart, using your best judgement, and not putting yourself in a situation that looks risky (e.g. sitting down/standing shoulder-to-should at a crowded bar).
All-in-all tho, IMO, theme parks and even hotels are fairly safe places to be when the right practices are in place like UO has done.