Hi! *waves* Here via est_meta (and I adore your layout, btw). I'm Sally, mun to Johnny Depp, Ben McKenzie, Jesse Spencer, and the shiny new Jared Padalecki. I don't have any girls in this game but my boys have played with them, and I run a girl pup in another game.

My thoughts are these:
If you're seriously considering bringing in a female pup, do NOT rule out the possibility of het scenes. As much as this is a slash-centric game, there has been quite a lot of extremely hot het in its history.
Having a pup who is not yet an Est member really doesn't pose as many problems as you might think. All the pups in the game (members or not) are on the journal system, it's just understood that "public to the Establishment" posts can only be read by pups who are Est members, whereas Est members can read everyone's posts (unless they're marked private). So it's still pretty easy to get a great dialogue going with people your pup doesn't know. In addition, so long as your pup knows pretty much a single other pup (who happens to be an Est member), you've got an in: just ping the mun of said pup, and work out a way your pup can somehow express an interest or a need, and their pup can (subtly) clue yours in about the Est. It has to be done right - no shouting from the rooftops *g* - but it can be done pretty easily.
That's my advice, use it as you like or not at all. My recommendation, on the other hand, would be to do both: First, bring in your male pup. Get acclimated. Get involved in the game and comfortable with it. Enjoy yourself. Then, once you yourself feel established lol lame pun ftw, bring in your female pup. It'll likely be a rewarding experience either way, but easier if you bring your guy in first.

Two cents! And welcome!