Are you also asking for advice on a good trailer sailer, or just have a live Montego 20 on the hook, and debating whether or not to get it?
Here's the sailboatdata sheet for it:
http://sailboatdata.com/viewrecord.asp?class_id=56
If you want advice on a similar fixed keel trailer sailer, try a Com-Pac 19
I think I rather fancy a ballasted shoal keel with centerboard style boat, myself, such as my O'day 192, or Precision 18. Going a bit bigger, there's the Precision 21. The West Wight Potter 19 is a beloved boat, but it has a lifting keel. The new International Marine Voyager 20 is based on the WWP19 hull, but has ballasted keel/centerboard setup.
That's almost one of the definitions of a trailer sailor, is no deep keel, for easy launch retrieval. To get enough center of resistance in a shoal keel without resorting to lifting keel, swing keel, or shoal keel/centerboard combo, you have to make the shallow keel longer, as in the Com-Pac 19, but I personally don't like the sluggish turning of a long shoal keel. The other way to go is a shoal wing keel, in boats such as the Catalina Capri 18.