Bonaire and Curacao are below the hurricane belt and less likely to get hit by a bad storm. It may be rainy at that time of year but usually not enough to ruin a dive vacation although the vis may not be as great as it can get - it depends. It is a fairly long trip from SF but since you are planning 9 or 10 days that gives you a little cushion. Sometimes the airfare is pricey but the diving is usually cheap. These are both lovely locations but you should enjoy shore diving to get the most out of Bonaire or Curacao although boat diving (and house pier diving) are usually also available. We like to stay at Den Laman on Bonaire but there are a lot of good choices on both Curacao and Bonaire.
We have been going to the Caribbean during late Oct and early Nov for decades to celebrate our anniversary and we have never been hit with a hurricane, but that doesn't mean it can't happen, and there have been trips when we've encountered storms, wind, waves, and reduced vis, but that can happen anywhere at any time. Another reason we like the Caribbean in the fall is because it is the low season, prices are at their cheapest and the destinations are not crowded. Also the water temperature is at the warmest, in the 80s; but you do run an increased risk of bad storms between June through November.
Roatan and Belize are also great destinations and others that have been there more recently can better advise you. Keep in mind that you will need to be careful about the drinking water and take vaccines and medications for malaria and other diseases like Typhoid and Hepatitis A when you visit this part of the world. Mosquito precautions are important all over the tropics but the incidence of dengue and chikungunya are higher along the mosquito coast than in some other areas of the region. I am not saying that you shouldn't visit, I have been to both Roatan and Belize twice myself, but these are additional factors to consider.
You didn't mention budget. And what are you looking for in a vacation destination? Are you mostly interested in sun, relaxation, and diving? Or do you also enjoy restaurants, sight-seeing, and topside amenities? Since you have 9 - 10 days you might consider a 2-island trip, or an island and a liveaboard dive vessel.
For instance, you could spend a few days on Grand Cayman to enjoy topside activities and then head over to Little Cayman or Cayman Brac for a week of relaxation and diving. I just mentioned the Caymans because you can usually find easy and less expensive airfare to Grand Cayman from all over North America and then it is another $140 for a short round trip hop over to the sister islands.
Or you could spend a few days on St. Martin, Provo, or Grand Cayman and then board a liveaboard dive boat for a week of diving. You do have to take precautions with the drinking water on Provo but not on Bonaire, Curacao, St. Martin, or GC. None of the destinations I've suggested are cheap but there are ways to control the expense and still have a great vacation and sometimes you can find good prices during the fall because it is the low season.
There are a lot of great dive destinations to visit in the Caribbean, St. Croix is another good choice with good boat and shore based diving and nice topside activities. Also, since you are traveling from the West Coast you might want to consider Hawaii or Cabo? Good luck!
