You can either stay in a first rate hotel or in the tourist area--but not both. There are no first rate hotels in the tourist part of TJ, assuming that you, like most people, consider the tourist area to be Avenida Revolucion and the Zona Norte.
There are many good hotels in the Zona Rio or by the border. These areas aren't far from the downtown area and ZN, but you'll probably want to use a cab ($5.00) although the distance is walkable. (Maybe a mile.) The Zona Rio is an upscale part of town (near the Cultural Center) with some five star restuarants (try Villa Saverios). You are safer there than downtown.
Decedent hotels have some type of security. It should prevent people from wandering around. In theory an escort shouldn't be able to get to your room without being stopped.
Not to worry. Hotels are very used to men having "company." (I usually register for two as it solves a lot of problems.) Nobody will think twice if they see you taking a girl to your room.
Many guys use the Pueblo Amigo hotel. It is near the border and very tourist friendly. However, it has a lobby. They are very "chica" friendly and you'll have no problem taking a girl to your room.
On Sanchez Toabado in the Zona Rio is the Hacienda del Rio. It has a typical motel setup. The chances are high an escort can get to your room (if she isn't dressed like a hooker) without being spotted. Obviously the closer you are to the parking lot the easier it will be (and the more noise you'll have at night.)
I like the Hotel Lucerna in the Zona Rio. It is possible to enter a room in the Anex at the back of the hotel through the parking lot. I'm sneaked chicas into by room using this route before, but obviously it helps to know the lay of the land.
Downtown at 7th and Madero is the Villa de Zaragosa; it's on the order of a Travel Lodge. So it also has a motel setup. There is a security guard wandering around so the chica may or may not reach your room without answering questions. This place is very chica friendly. (They've been known to also help guys find companionship.) If you stay at the VZ do not use a credit cards. The clerks there are infamous for collecting and selling credit card numbers.
The hotels in the Zona Norte are very used to having chicas come and go. They are, however, of the lowest quality. The Leva is often used by mongers staying in the Zona.