When I lived in America, I learned that minor league games were lots of fun and much less expensive than major league games. Granted, minor league teams have always played further away from my home than major league teams
When I lived in Atlanta I had to head to Rome, Augusta, or Columbus before the Gwinnett Braves game to town. In San Francisco, the Giants were just across town and the A's a short train ride away; the San Jose Giants took a long time to get to.
But I always made it a point to visit a few new stadiums every year while on road trips, and stop by the more-local stadiums at least once a season.
Moving to Japan, I had a new goal: to visit all 12 of the major league home stadiums (something I completed about a month ago). I also considered going to minor league games, but after two years I've only been to one game.
Oh, and don't think about getting foul balls; they come by and collect them as they fall. I'm kind of disappointed by that policy (especially with the women's league, which has paid tickets). I'd love to have a game ball if I get lucky from a minor league team. Granted, admission to this stadium is free.
Minor league teams almost never play on Mondays - NPB's major league teams rarely play on non-holiday Mondays either. That makes it pretty tough to get to games when crowds are light for me. But I might be able to visit again some time next year; I'd like to get to a few more stadiums as I travel.
I suppose I should mention that Lotte Urawa Stadium is used by the Lotte Marines' farm team.
In the fall (about three weeks in October), the Phoenix League "expands" the season a bit. The games all seem to start around lunch time.
The stadium is located near the Saikyo line tracks a bit of a walk south from Musashi Urawa Station. You can't miss it if you follow the tracks on the west side.