You are asking the right stuff make sure to relax and enjoy yhte suna dnwater while you are there.
1. Which is best - Mi Dushi, Octopus, or Jolly Pirates
I would say Mi Dushi or Octopus dependent on your preference. Jolly Pirate is a blast, more of a party, with a bigger crowd. Octopus is more of a sleepy sail only ride, only a dozen or so people, and more intimate. I like both.
2. Good anniversary restaurant?? Madame J's or another one? We had an excellnt meal at MJ's last month.
3. Best cell phone rental agency? Don't know used our verizon world phone.
4. Rent a car or take bus and taxis?? Buses are excellent and regular for trips, I would use a taxi to dinner or if in a hurry.
5. Is ABC Jeep tour worth the day? Absolutely! We did this trip on our first visit to the island and it was the best way to see the complete island in a day. It is tiring out in the hot sun all day so bring a hat, sunscreen, your bathing suit!
6. Best place to buy a few groceries? Ling and Sons There are four grocery store in a two block area all are a bit different, we usually shop at Lings.
http://www.lingandsons.com/ling/home.do
There is an unlabeled store, Super Foods to the left of Hong Kings
http://www.wikimapia.org/#lat=12.530...18&l=0&m=a&v=2
Where are you staying?