My wife and I have done two trips to Bonaire. Both times we stayed at Airbnbs, and never once wished we had gone to one of the diving resorts. We rented pick up trucks at the airport, rented tanks from local shops, and did all shore diving, and enjoyed it enough that we are doing our third trip in January. My wife typically only does one dive trip per year and was a little weary of going without a guide, but quickly realized that it was easy enough to guide ourselves, and she enjoyed the empowerment that came with that. And a big plus of staying at an Airbnb was that in addition to enjoying the local restaurants, we did a lot of cooking, having bought groceries at a cool Dutch supermarket called Van Den Tweel, which has great Dutch cheeses, breads, sausages, etc.
Most dive sites in Bonaire are very easy to enter/exit, tend to have little current, and are easy to navigate, as others have described. But do exercise common sense. Some of the sites have more challenging entries/exits and current (Karpata, Hilma Hooker, Red Slave come to mind), and variable conditions. Ask at the shops for advice about particular sites you are thinking of diving. Get multiple opinions. Ask other divers coming out of the water what they experienced in terms of current, and entries/exits. And just err on the safe side. The first time we went to Karpata, the seas had picked up, and the entry looked iffy, so we left it for the next day, and went diving elsewhere. We returned the next day to Karpata and the seas were flat, so entry/exit was a piece of cake.
I definitely would not get a guide to dive Salt Pier, as it's an easy dive provided seas are calm. What I find interesting about the pier is that most divers seem to keep away from the pilings, which are just absolutely encrusted with life and are one of the big attractions at the pier. Unless there is crazy surge, or you have really lousy buoyancy control, you should take your time at the pilings and inspect the incredible life on them.
This is what the pilings look like from a distance:
And this is what they look like up close:
Happy to answer any questions or provide Airbnb recommendations.