Bonaire is known for its great shore diving, so if you go there and want to take advantage of that aspect, you will need to find a buddy and be confident of your dive planning and navigation skills. Keep that in mind.
I am going to agree with Dennis and disagree with some of the suggestions from other posters.
My wife is an avid snorkeler but a non-diver; consequently, we vacation in places that are good for her and good for me. I have therefore done hundreds of dives in many locations as an unattached diver. I am quite used to it, and I have some suggestions.
In general, if you choose any location that focuses on boat diving, you should not have a problem. It is really easy to walk onto a boat as a single diver and find someone to dive with. It happens all the time, so people are used to it. In many cases, if there is a DM involved, he or she will make sure everyone is buddied up. In some places, like Cozumel, DMs are required, and everyone must stay together as a group. Sometimes you have a specific buddy; sometimes you don't. The important thing is to scout out the area ahead of time and pick out the operator who is right for you and your level of ability. Some operators cater to beginning divers, some operators cater to advanced divers, and most are somewhere in between.
Things can be different if the area focuses on shore diving. Before I went to Bonaire (about 8 years ago), I scouted things out carefully by participating in several dedicated Bonaire forums. I said I would be going as a single diver, and I asked for and received advice on getting buddies for shore diving. When I arrived, in our orientation we were told that our resort had a system for matching up single divers so they could buddy up on shore dives. They also said that if we were having problems getting those dives, we should contact them for help. I used their system, and I made zero contacts. I guess I was the only unattached diver there--it sure seemed like it. I believe every other person at the resort was part of a group, and those groups all had plans of their own. I had bought a package that included a certain number of boat dives, and those were no problem. I did get some shore dives in with some of the people I met on those dives, but it was not easy. The helpful tips I got from the forums yielded one shore dive. I contacted the management at the resort for the help they promised for those having trouble finding buddies. They told me to purchase more boat dives.