Taxis to St.Petersberg Airport ?

Hi!
Yeah, I do have some experience with that - but I'm not sure if it is relevant.
For starters, where is your hotel?

I’m on the Rick Steve’s tour for best of St. Petersburg, but they haven’t told us what hotel we’re in yet. I was just concerned that I might not be able to reserve or get a cab at 3 AM. Never been to Russia before.....

One of the reasons I asked was that most major bridges in SPB are drawn at various points during the night - and if your hotel is located, for instance, on Vasilievsky island, you might be looking at longer time in transit.

If you are located somewhere in the tourist center (Centralny District, Admiralteyski District, etc), your ride at that time of day should take about 30 to 40 minutes.
You could most certainly ask the hotel to make a reservation, but you might be better off using one of the many ride share services (Yandex, Gett, Taxovichkoff, Citymobil, Uber, etc). If you download one of their apps, it will give you both the costs and the routes and the expected wait times - just don't push "order now" button just yet.

One last thing - Pulkovo is a relatively small airport, but I would still allow for at least 2 hrs before an international flight, so if I were you, I'd probably be leaving a bit before 3 just to be on the safe side.

Perilofp is correct.

It mostly depends on the side of the Neva river your hotel is located. Otherwise, 2.5 hours before your flight is more than enough to be on time. I've used Pulkovo about 5 years ago with the same time span and had no problems. However, I was flying to Minsk and used local flights area of the airport, Belarus and Russia do not have "real" border control between them. I would suggest to leave your hotel at 2.30AM in case you're afraid you can miss the flight.

Regards

We asked the hotel to arrange an early morning airport taxi. They had several people they knew who were reliable. I imagine if you speak with the front desk when you arrive, they can set a ride up for you.