Almost any location within the city limits is within a 15 minute drive, even with traffic if you know how to navigate streets.  Most places in the North, South and East county are with in a 30-40 minute drive(depending on traffic).  There are also a lot of Condos/Apartments in this area as well.  Access to every major freeway in the county is readily available.

If I had to limit myself to San Diego I would agree with Mike that Mission Valley is the best area.  It's the most central and accessoble.  But...since I live in North County, I would prefer something further north along the I-15 corridor - say RB or Escondido.  Of course, next door would be ideal!

It's a great central area, parking's not too bad, easy freeway access to any direction, and not so residential as to attract attention.

Should quit while I’m ahead.  Those who don't know what EOM stands for, please read on:

Sedona, FWIW, I think other than price and location, an incall should have its entry/exit point discretely located (not everyone loves a parade...).  Quality of construction might be a factor – single pain windows and 4” party walls might meet the building code but are pitifully inadequate if you’ve got plug & play happening on the other side.  Off-site management, on-site security would be value added for the hostess' protection and piece of mind.  The lease should permit "one dog, any size."  (All visiting gentlemen should say “hello” to the hostess’ Rottwieler/Shepherd/Pitbull-cross on the way to the bedroom.)  Nearby reserved parking would probably also be a plus for gentlemen 'on the go.'

for us N. County guys?

'central' to me would be area that includes UTC, Sorrento Valley, University City and east to Kearney Mesa.

Seems like you have two camps..."traditional San Diegans", who view San Diego by its city limits, and North County types, who view San Diego by the county limits.

To be as central as possible for those in North County, you would probably have to go a bit north of Mission Valley, which is considered "central" for the "traditional" camp...maybe at least Clairemont or Tierrasanta, if not all the way to the University Towne Center area.

However, the bottom line for someone as well received as you are, hon, is what another guy already said..."If you build it, they will come"...no matter WHERE you build it.  

Good luck.