Given the new NCAA rules, teams are going to have a good number of "nonscholarship recruits" (or "recruited walk ons", whatever term you prefer), as these guys "nonscholarship recruits" will be treated just like any other recruit but the difference will be these 6 or 7 won't receive any money, but are part of the team (listed on the roster). Being in this status does present some uncertainty for the player during his time on campus, but most coaches are honorable men and won't dump a player for the sake of another. But, when you factor in injuries, travel costs/player, etc., the nonscholarship player is the "most expendible" should there be any extenuating circumstances. (Again, though, most coaches are decent men and generally wouldn't treat you this way).
Given this new scenario, simply showing up on campus and attending a tryout is likely going to be that much tougher as coaches will likely already have some kids filling in their nonscholarhip roster spots (which depending on the next couple of years changes from ~6 to ~8). The best situation for trying to walk on is to take the advice given above, but also learning about the number of scholarships the team may have to work with (i.e., an underfunded program). So, while it won't be anything for the major D-I programs, there will be a lot of other D-I programs that have to deal with fewer than the max NCAA allowed scholarships, therefore with the new 25% minimum these schools will depend on more nonscholarship players to fill their rosters. If it is a public school, check out the athletic budget or ask the athletic office about the number of scholarships for the baseball program. Then you will know where to set your sites.
Good luck with your choice; be diligent in your research of programs as you explore this option.