I agree on not calling 911. These are not emergency situations (calls)!
As for panhandlers, unless the city or county has an ordinance prohibiting such activities or requires that panhandlers carry a permit as some agencies now require, it is left up to the property owners (or representitive thereof) as to how they deal with it. Now if they do ask the panhandler to leave their property and they refuse, then local law can be called in on a tresspassing complaint and remove said panhandler.
Since prostitution is illegal (except in Nevada where it is regulated) the rules are different. The truckstop has an obligation to report illegal activities on their property or face possible fines themselves. Not all do! Many try in the beginning only to give up on what they feel is fighting a loosing battle.
So, do as we've done, call into the fuel desk, report the illegal activity, and ask who the local law agency would be that patrols their area. Then if they can't (won't) provide you the number, call information and ask for their NON emergency number. Then make the call yourself to request that a unit cruise the lot. Provide a full discription and location (name of last truck seen getting in) to help aid in the apprehension of the prostitute. That is how you clear the vermin from the lot with clear conscience knowing you just helped make the lot safer for you and your fellow drivers!
All of this takes less time than she will take servicing a John!
You won't believe what happens to the prostitute, driver, and the truck when the local law comes a knock'n and catches them in the act! Explain to the boss why the truck just got impounded! LOL Better yet, imagine having to explain to the wife why they're in jail for solicitation of a prostitute! NOT good.