Re: provisioning Panama- Tahiti, Currently in St Martin.
There is an excellent place to provision in Panama City at the Pacific end of the canal. There are a couple of branches of a 'warehouse' style store, like Costco in the US and the name escapes me but everyone will know what I am talking about. They are not close to the anchorages so you will have to take a cab, at least on the way back. Buses are fine but time-consuming.
You need to buy a membership to use the store and it works well if you split the cost of membership with other cruisers, Prices are incredible. One litre boxes of OK Chilean wine are $2 and beer is $9 a case. This place is only worthwhile if you are buying a lot of stuff. We went with a couple from another boat each of us absolutely jammed cabs for the trip back. Buy lots here as you will not get anywhere near the prices elsewhere.
If you are at the marina in Papeete there is a hypermarche that is within walking distance and it may be the best supermarket I have ever seen (huge, French, in the middle of the ocean on a tropical island). Prices are very high though. There is a fine traditional market downtown with excellent produce.
Finished the circumnavigation in early February in Grenada. Have to work on a book project for the next several months so the boat will be waiting for next year.