Mt. Lebanon - no overnight street parking??

This is news to me. I’ve lived here for a year now; have parked my car on the street for the entire year and have never received a warning/ticket. Woke up this morning with a warning on my car for parking on the street overnight. I called because I was so confused. There are no signs on my street explaining any parking restrictions. Apparently in Mt. Lebanon, you cannot park your car on the street between 2 and 6 am. One of my neighbors is apparently a narc and called and complained that the cars parked on the street aren’t get ticketed. I have a parking spot, but for reasons I don’t feel like explaining I haven’t been parking in it. I will be now, but I’m wondering, what do I do if I have friends sleep over?? Where are they supposed to park? I don’t want my friends getting ticketed. I appreciate any suggestions!