We are staying at the Plaza Resort for 2 weeks in March and plan to dive every other day and vegetate on the beach the others. This is our first visit to the island. Do we really need a rental, or are we better off taking a taxi for restaurants and renting a moped or other vehicle if we want to do the occasional excursion? Thanks for the feedback

Unless your planning on doing all boat dives you are going to need a car for the shore diving. The island is small, but not that small. Check the prices, but I think its cheaper to rent by the week than by the day. A car gives you the fredom to explore the island and have access to everything.

Since you have two weeks, just rent a car the first week. If you don't use it much, return it at the end of the week. If you can justify the need, you can make arrangements to keep it another week.

hard to imagine bonaire w/o wheels for shore diving trips... todd's idea sounds good... however, i've spent vacations perhaps the way you've suggested, relaxing at a resort, using on-site recreation, beaches, etc, and venturing out now and again... so i could see renting specific days only, IFF you aren't opposed to extra rental transactions or walking/taxis to off-hotel restaurants, and your hotel has plenty of what you came to do... i would use $50/day as a benchmark for renting basic transportation, or the daily rental fee, like $30, $40, or $50, multiplied by 1.7 to cover all rental costs.

what follows is not necessarily criticism [hey, they are running a business] but might save some sticker shock, or give an idea of the real costs of renting a car on bonaire...
don't be surprised when your $180 weekly rental is $520 when you're done... our ABCarental deal was $180/wk & $30/day... in the USA our USAA insurance covers us on rentals, but they didn't cover it in bonaire, so we bought $10/day insurance, which btw covers nothing basic, like flats, 5mph f-benders, broken windows, missing or stolen parts, scratches, etc, in fact, ABC rental had us sign a form that lists a full page of normal "incidents" that they will not cover, in addition to the full page of fine print disclaimers on the back of the rental form... this car rental kiosk and legal disclaimer was our first transaction in bonaire... welcome to paradise and peace of mind... it basically covers only major damage/injury, one would hope... anyway, here's what it really cost us, itemized:
1 week @ 180/wk = $180
4 days @ 30/day = $120 (2 days were from airport arrival at 10pm, and departure day at 6am, so if the hotel shuttles you, you've saved 2 days)
11 days insurance = $110
5% O.B.??? = $20.50
11 days @ $3.50/day govt tax = $38.50
totaled = $469
gas ain't cheap either, we spent about $50...
so the total total was around $520, or ~$50/day.
the good news... yeehaw, you get unlimited mileage, so have fun racking up miles on the 8-lane 70mph expressways

But exploring the island just driving is sure a great way to off gas. My wife and I just love driving and exploring between dives.

But exploring the island just driving is sure a great way to off gas. My wife and I just love driving and exploring between dives.

oops, this is what happens when work gets in the way
Aquaman