Towing Problem Tenants

[Kyle M.]

I have a problem at my 3 unit multifamily property here in Pennsylvania. I am at the tail end of a lot of renovations on the property and moving in new tenants to some units. When I purchased the property I only inherited one set of tenants from prior landlord (the problem tenants). There are 2 main problems- first, the guy is either subletting to somebody or just randomly moved another adult in (that is not on the lease). Second, that person is parking her car (with a broken window that has a bag taped over it) in my parking lot and the family is taking up more than their allotted parking spots per their lease. Now that I am moving new tenants in, this is a larger problem as there is limited parking space and these people do not listen. 

Do I need to have towing signs posted on a small residential property like this to tow their extra cars? Can I just tow the woman's car since she is not even listed on the lease? I recently sent them in writing a notice to quit or vacate in 30 days for the 2 main violations- parking and illegal subletting and I have also terminated his month to month lease that he came over with from the old landlord.