I go early early, EARLY morning and use the cleanest area I can find in a local park.
The downside is somebody probably played soccer/baseball/football there yesterday. The upside is I NEVER had to teach crosstracks lol
At one point, we lived close to Fort Wadsworth
which was just great! Lots of grass, and only one ball field. The rest was unused, until we found it! I think we had the best tracking there, and don't think we would have done so well on the 2 and 3 tracking without it
Basically I'll go at 5am, lay my track, go home, wait about an hour, get the dog, and run the track. Only a handful of times did I come back to a ruined track at that hour.
P.S. we used to live in NYC, now Denver. There are LOTS of nice places to track here hehe but totally different terrain.