As small as Bonaire is we have found it pretty easy to play phone tag in the morning if we have not set up the morning plans the night befor, or if the plans are sketched but not final. Then do the phone thing during lunch/SI from our rooms or hotels. Again if we have not set up a lunch get together already, at which afternoon and evening plans are discussed. Unless you go further north where it's the long way home, the island is so small it's pretty easy to get together and mix and match dive parties on the fly this way.
If the room doesn't have a phone rentals are available but I would not leave the phones in your vehicle (I have, but not about to say online where I stash it!)
If the room doesn't have a phone rentals are available but I would not leave the phones in your vehicle (I have, but not about to say online where I stash it!)