Tip from an old pro, given to me....
Best Two Ways to avoid looking out of place for incall clients.
1) hide a room key under your wiper and make sure to park where you can see your car. Tell them where to find it and then to call your number. If you still feel safe you answer and give them the room number. If not, tell the hotel you lost your key and ask them to rest it. Just don't "lose" your room key to often.
2) be outside in the sunshine or just talking a walk around, know what he is driving so you can appear to know each other and then walk in together. Always enter from a side or back door that doesn't draw attention from the front desk staff.
After my brush, I started doing one of the two and haven't had any problems or felt unsafe anywhere I have gone.