There's nothing more suspicious than using the back door
Anyway it's not illegal, just go about it like normal.
RE the love hotels - obviously they're not soley for the purposes of fucking 141 girls. Many a time I've visited a love hotel with my girlfriend early on in our relationship when we weren't living together and sometimes it was the most convenient option (or we were too drunk to make it back from Kowloon to HK island). And of course then there's all the politicians and businessmen shagging their mistresses in the love hotels. So they're not strictly dens of sin or anything, just a damn shame there aren't more in the world.