Gus:
I can't really 'recommend' it yet as we haven't gone, but I've booked the wife and I for a 7 day (5 dive day) liveaboard trip on the Juliet leaving Puerto Rico's west coast and doing a Mona Passage route, for July. They still had some openings in August when I spoke to them last. Juliet takes only 12 passengers, 5 crew, and our cost was $430 airfare direct from DFW to San Juan, then $1500 for the week diving (includes all food and lodging onboard of course). We added another $300 each for hotel and will stay 3 extra days on PR after the trip to drive around and see some topside scenery, but that really wasn't necessary...there was also an overnight on the way in just to be safe with connections getting to the port from the airport. Rental car gets you from San Juan to Mayaguez (where the Juliet ports) for about $45 one-way rental (return at Mayaguez airport).
Although we'll have some additional spending for taxi, (after dropping off car), food on PR, and maybe sundries (translation: I bring as much rum back as I can from San Juan, as there's some inexpensive local brands they don't sell in the states and no import duties as you're already in the "U.S." for all practical purposes), but my total budget was $5k for the two of us.
Juliet's site is www.divejuliet.com, although you'd probably have to email them to find out any remaining availability for this summer. This is the first season they've done the Mona itinerary, and I couldn't find out a lot about it aside from the rare trip report from some of the Nektons which do Mona in the winter.
I'm with you - 2 dives/day is too little, but doesn't really leave enough time to do something good with the remainder of the day. 5 might be 'too much' for more than 2-3 days (we also do the Flower Gardens 3 day trips when we can, and those itineraries are usually 5/4/2 dives per day...but I'd like the opportunity to be there at least. I've also got right around 90 dives and just one real 'photography diving' trip under my belt. And I'll be equally interested in the other responses you get. Seems to me that I'd love to do the S Pacific or Indonesian sites, but the airfare and time change means I need to subsidize that over at least a 2 week trip to make it worthwhile, and that gets pricey both in terms of coordinating time off and overall cost. But 'cheaper' trips usually equate to 2-dive dayboat sorts of things which makes me feel like I'm wasting the hassle of all the gear packing and transporting.
One other liveaboard option I can think of off the top of my head that's cheaper than you mention in your OP is the Spree, which now dives the Dry Tortugas in Florida. I think they run like $1500 for a 5 day trip, with like 4-5 dives a day available. So your airfare stays domestic, with a taxi ride to the dock. Captain Frank and DM Melanie are great folk, highly recommended. I got to dive with them a couple times while they were in the Flower Gardens market before moving to FL this year. www.spreeexpeditions.com
Neither idea meets a $3k / pair for a week including airfare though. I don't know where you'll find that - with Boston as an origination point - unless somehow frequent flier miles are involved!! (That's the way I afforded Dominica
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