When the game lets you choose one of the two to follow, I followed the Stormcloak guy, but I'm starting to wish I had followed the Imperial. Can I still ally with the Imperials later in the game, even though I didn't follow the Imperial guy?

When was this? At the start when you were a prisoner?

Ya you can. I was worried about the same thing since I followed the imperial guy (he was the one who saved me after all that stormcloak bastard saved his own skin). I found a stormcloak camp later and had the option to join. Haven't decided which i'll do just yet.

Yes, you can still join the Imperials. There's an Imperial in Falkreath, speak to him and you will get a quest sending you to Solitude.

I was surprised that I was asked to join the Imperials so early into the game. I'm waiting until I learn more about the conflict...it's almost as bad as going to the polls on election day and knowing nothing about the names on the ballot other than who's a D and who's a R.

It's definitely ridiculous for the first playthrough. I guess it's a nice touch if you know what your character is going to be beforehand. I'd rather just start at the exit on subsequent plays though.

The civil war is separate from the main quest, so it's not even necessary to take part in. I think I'm gonna wait for my second playthrough to get involved in any of that.

Who you go with makes very little differeance, AFAIK. You'll just get the quest to join one faction or the other a little earlier. But, overall, after you get to riverwood, the exact same thing happens, just with differeant people. After leaving River wood, I've notice absolutly no differeances, I have a character that chose the Imperial, and one that chose the Stormcloak, and by lvl 20 havn't seen anything that it has changed.

As soon as you leave riverwood by road, you may encounter some wandering "Farmer"s and they will give you the quest to join the other faction.