Wow, I'm not sure how I missed your post. I'm sorry
Most of our 40k gaming is small group based, with groups coming in to play on Wednesdays and Fridays most frequently. We run tournaments once per month on Sundays, and we've got an upcoming national Apocalypse campaign called Lucky 13s which should bring players in on at least two Saturdays per month starting in May.
If you'd like to be sure you'll have some games to watch, I should be scheduling some in about a week. If you'd like, I'll let you know when I'll be down so that you can get used to the newest rules and the pace of play. If you bring in your army we can probably get a quick game in as well.
As for your choice of armies, you should know that Sisters models are getting harder and harder to find, and almost all of them are pewter. While we are still able to stock basic troops, HQs, and a few more specialised units, we can only order about half as many kits as we can get for other armies. You shouldn't let this deter you, as the models can be found (and hopefully GWS will eventually release some new ones), but it is something you should be aware of.
Of your wife's choices, Marines and Orks have the newest codices. Orks seem to be very popular and powerful recently, and marines are always a safe bet for new players. Eldar units are more expensive points-wise, but you can find flexibility in Eldar lists that is hard to match with other armies.
While a painted army looks much better on the table, I wouldn't worry about finishing before you get your first games in. We have enough new players in the store that it's not uncommon to see grey plastic on the table. Some players can also get burned out by spending long hours painting and modelling a unit, only to find that it doesn't fit well with their playstyle in practice.