If you're going to the Crowne Plaza, then the lot at restaurant row is fine. Same thing with the Residence Inn and Sheraton in the general area. Obviously, you're not going to walk from Carlson Court to the Holiday Inn at Dixon and Martin Grove especially in the winter. It would be a lousy walk even when the weather is nice.Restaurant row on Carlson Court is good is the incall location is at Crowne Plaza, but it's a 20 min walk from Holiday Inn, not worth it.
I want to park at the restaurants lot near Toronto Congress Centre as well but I'm concerned about those nosey owners calling a tow truck, last thing I want is to come out of my one hour appointment and notice my car not there. Many years ago I made a mistake of getting into the lot of Park'N Fly thinking it's just a paid parking lot and almost got my car trapped there, I had to explain to the guy working there I made a mistake, and was able to get out 10 minutes before my actual appointment.
Someone also mentioned the auto shop behind Holiday Inn after they close, but I don't want to risk getting a ticket for parking unauthorized at private property, got this bullshit ticket in Mississauga at Webb Dr after parking at that stupid field to save $1.5.
It's definitely not a good idea to park at an auto shop or strip mall that has few cars around.
I've also gone to an incall on Webb Drive in Mississauga. There is metered parking on that street so I don't know why you chose to park in the field. I don't think it's possible to park in the field because there should be a concrete barrier that blocks access. You're were clealy not paying close enough attention to the various signs around. There's plenty of parking at City Hall and Square One.
I don't know how you accidentally parked in the Park and Fly lot because it has a giant sign, booth and gates in front.