Your thoughts on Albergs and Islanders appreciated
You are really asking a very complex question. With all due respect, the very wording of your question is full of all kinds of very basic misunderstandings and perhaps suggest that you have a bit more homework to do before you are ready to cruise a remote venue like much of South and Central America.
Starting with the basics, In your post you say," Statistics such as low Capsize Ratios (<1.9) and "Motion Comfort" numbers (>30) are important to me". I am not sure what you know about these surrogate formulas but neither have any real use in predicting the behavior of any particular boat. If you look at the actual variable factors contained in these surrogate formulas, none of the factors that actually predict stability (vertical center of gravity, ballast, hull form, etc) is contained in the Capsize Ratio and none of the main factors that impact comfort (weight distribution, waterline length and beam, overhang length, vertical center of gravity,draft, mast height, hull form, etc)are contained in the Comfort Index. The numbers that come out of these two crude approximations should have no bearing on your decision between boats without doing so much more additional analysis that the ratio and index number becomes worse than meaningless. In the worst cases, these numbers are so misleading as to be dangerous to even consider.
Then there is the full keel issue. While full keels have some advantages when cruising in remote areas, (for example, beaching for maintenance is easier) and in theory they have better directional stability (i.e. they theoretically track better) none of the boats that you mention really have full keels. With the exception of the Islander 36 and Islander Freeport 36(which are both fin keel boats) and the Islander 38 (which I beleive came in two models, one of which actually has a shoal draft full keel and the other was more like a Brewer notch fin and skeg rudder), the other choices have very cut away forefoots and have sharply raked rudder posts located pretty far forward in the hull. These are really not full keel boats at all, and frankly offer none of the advantages of a full keel (better tracking and rudder protection and ease of beaching) or a fin keel (better speed, windward performance, manueverability and lighter helm loads) with almost all of the disadvantages of both keel types. In the case of the Alberg 35, you have the worst of all worlds, a fin keel with an attached rudder(by the classic definition where a fin keel is a keel whose bottom is 50% or less of the length on deck or the length of the sail plan when the sail plan is in excess of the length on deck).
Quickly running through the list of your current choices:
Alberg 35: These were nice looking boats but having spent a fair amount of time sailing on them they really are not my idea of an offshore cruiser primarily on the motion comfort issue. The Alberg 35''s began life as CCA rule beating race boat. As a result they have a ridiculously short waterline length for a 35 footer. While you are not concerned with the adverse impact of this short waterline length on the boat''s speed potential, the bigger problem with these boats is thier tendancy to hobby horse, especially as loaded for cruising with a heavy anchor and chain rode and a lazarette filled with gear. Also the deep canoe body on the 35''s result in a pretty rolly motion (which some people prefer but which many people find quite uncomfortable). The narrow beam on these boats means that they are really pretty tender and so are sailed on their ear in significant breezes.
Alberg 37: Much of the above also applies to the Alberg 37''s, except that they were more moderate in waterline length and beam. I would avoid the 37 yawls partially as a motion comfort issue and partially as a structural issue.
Islander Freeports: These are hard boats to classify as they varied in design from one length to another. In a general sense they are reasonably good distance cruisers. They were budget oriented and so some cost cutting items may come back to haunt you (hardware, rudder construction and mast support structure). I would personally want to do something about the large plexiglass cabin portlights if I were taking one offshore.
Islander 36: These are neat boats and have a lot to offer but again, they began as race boats and so were shaped more by racing than by cruising. This was an era when lighter weight race boats such as this, really did not tollerate carrying the kinds of heavier loads that are commonly associated with distance voyaging. That said, I have run into folks who have very successfully cruised them over very long distances. (By the way, the same can be said for the Alberg 35, and Alberg 37).
The ice has finally melted on the creek so I''m heading out sailing. Good luck,