Does anybody know how the DiMaggio League rates in terms of exposure and caliber of play?

I assume you are asking about exposure to college coaches. In our experience, whether you are playing Joe D or American Legion on the Peninsula, those games are unlikely to get any exposure with the local 4 year college coaches. You may find one or two who show up for some games at the end of season tournament, but it is rare to non existent they will show for any regular season games.
This is not a reflection on the quality of play. The top teams play pretty decent baseball. It is a reflection that college coaches use summer camps, showcases or travel team games for recruiting potential players