I dove my Drager Dolphin for 3 years with 250+ dives before I got trained on an Inspiration last summer. Rebreathers are expensive, cost more to run, more to maintain, more to travel with because you will always be over your weight limit / baggage limit. I don't think the Dolphin is terribly complex to dive with (compared to my Inspiration). If you've been ceritifed for adv nitrox you've already completed half the course. The Dolphins are more readily available as rentals around the world than any other rebreather, but you need to do your research before you go. Many of the Aggressors have them. And more resorts are starting to support them. You can travel with all your cylinders and divesorb, but the hard part is getting the rich nitrox mixes you will need. Most places won't blend above 36% and you will need 40-50% depending on the diving you do and your dosage config. I dove mine at 45% pretty much all the time, but that's a custom blend that I either mixed myself (yes, I'm a certified gas blender) or had to pay extra for because it has to be done by hand with partial pressure blending.
I would not recommend getting certified unless you are committed to buying one and diving one regularly. Rebreathers take practice and will take you about 20-25 dives to get really comfortable with them. I hated mine when I first got certified and thought I had wasted my money, but once I got it dialed in it was a dream. It's quiet, you breath warm moist air, extended bottom time, you get the physiological advantages of breathing richer nitrox mixes but you also have the depth limitations of the same. You won't be comfortable with it unless you use it regularly. And renting them isn't cheap, up here it's about $100/day. I tried the rent it and see if you like it routine and spent almost $1000 extra had I just bought it from the beginning. Some places will include training if you buy the unit from them.
However, once you get used to it, you'll never go back 
With all the overhead and hassles you need to deal with on rebreathers - I never dive open circuit anymore unless I absolutely have to.
As far as training goes, Tom Mount in Miami is one of the most experienced RB divers in the world and can train you on just about any rebreather ever made. Sunset House in Grand Cayman is also excellent. Erika Leigh-Haley is the former head of IANTD Canada and runs their dive shop now. I also visited Dive Tech in Grand Cayman and while I heard very good things about them, at the time I visited their RB instructor had just left so I don't know who's doing it now. In California I got certified at Scuba Schools of America with Rusty Berry (Trusty Rusty), he was very thorough and my open water dives were on a weekend livaboard in the Channel Islands.
Here's a very good Rebreather Article by Andrew Driver that was in Divers Magazine last year that talks about many of the rebreathers on the market today.
If you do decide to go rebreather, go with a good local dive store that's committed to rebreather diving. You'll need/want the support for service, supplies and consumables. And you'll want to build a relationship you trust where you can ask questions and trust the answers you get. The more you dive it the more questions will come up as your expertise increases.
Here's some other articles that are well worth reading. These are actually required reading for the Inspiration Class.
"What is a rebreather?" by Richard Pyle
"A Learner's Guide to Closed Circuit Rebreather Operations" by Richard Pyle
this one's not required but is also a great rebreather article. I would expect almost anyone who visits Wetpixel knows who Howard Hall is.
"Closed Circuit" by Howard Hall
