I got into NS2 recently and I have been thinking about jumping into competitive play. I have a team of a few friends, and I don't know how well we play yet, but I don't expect that we are especially good. My question is, when should we start joining the ENSL leagues, and at what level?

Just sent you a PM, missclicked instead of doing a post:)

Well, Season 3 already started and will last until November, you can't join the season if it's in progress.

You should start practicing playing pcws against other teams and join Season 4 which should start on January 2014.

Also, between Season 3 & 4, this is, from November to January, there will probably be one or a few ENSL cups in which your team could play.

Enjoy the game!

Add me on steam - we will play a couple of PCW's if you like to get you up to speed?

Start now, play scrims now. Start in season 4, or one of the upcoming cups.