I play RTS games waaaaaaay too slow for most online matches.  After getting my ass obliterated 4 times, I finally got an opponent in my last practice match that was like me, so I finally got to just sit back and turtle up, then pump out some huge units.  While the conflict between my legion of marines with 6 Thors and 2 Battlecruisers and his Ultralisks and other creepy crawlies was pretty awesome, there's way too much rushing and stuff in most matches for me to keep up.  Is there a way to play just against AI right now, or is that just gonna be in the final release?

Don't worry if you're not any good. Focus on learning unit strengths weaknesses, effective scouting techniques, proper economy management, etc. You (hopefully) learn something new each game. Watch some replays, get to understand why you got obliterated.
 
Or, play another game that's not a lame RTS. I mean no one plays these to have fun.

You can play against AI but only on Very Easy, start a custom game and add an AI bot. 
  
I don't really know much about knowing much when it comes to Starcraft but it sounds like your just sitting back and not expanding, which I certainly did in the very few games of SC1, which I lost. 
 
There's always going to be a bunch of resource fields on the map and if you don't go out to grab them but your opponent does he's going to have 3-4-5x the amount of stuff to play with and you can't win like that. 
 
Easiest way to learn is probably just to watch your own replays. (You can do that right?) Play a game, and if you lose just see what your opponent does that screws you over, next time be ready for it.

Starcraft is a pretty fast paced game. Maybe too fast for some players. To each their own. That's why there are other games by other companies for other types of people.

Just mess around with the map editor. They haven't allowed custom games yet but you can still test maps that other people made.

" Just mess around with the map editor. They haven't allowed custom games yet but you can still test maps that other people made. "

Blizzard mentioned somewhere that they currently have a matchmaking problem with the bottom 3% players. Hopefully, they'll get that fixed up by launch, and you'll be able to play against others who are at a similar skill level.
 
The current AI won't be of much use to you. It's only very easy, and it is *VERY* easy. It sends literally a few units to your base, and that's about it.
 
Try playing custom games with friends and turn the game speed down. That will help you to figure out what you need to be doing on a slower scale, so you can get a decent build order down, and then progress to faster speeds.

Yeah, all Ladder and most custom games start on "Faster", which, if you're used to playing on Fast or even, god forbid, Normal, Faster is insanely fast and requires you to really pick up your game. If you feel everything is moving too fast and literally think everything needs to sloooooooow down, then try a few games on Fast. Starcraft II as a beta is really no fun for players getting into the RTS scene, or even poking around. It's crazily competitive. I played a dude in Bronze when I was playing around in Custom, and that dude was serious! If you feel too overwhelmed, don't hesitate to chill until release where there will an excellent Single Player as well as a heavier player base to wade in as well as the Challenge Mode, which could help you hone your skills and learn to move and think faster in a game.

They've actually increased the speed again since this post. It's quite hard to keep up with how fast you gain minerals if you're a new player.

Watch a lot of games on TeamLiquid, mostly the HDH Invitational going on right now, as the pros are using everything to win that money.  You'll learn a lot of tips and standard build order that way.
 
Watch a lot of SC2, and learn face the CPU for Build order....and then take it to the real game.  I fucking sucked at SC1, but got better after about a month of getting my ass handed to me non-stop.

I play similar to you. I love to just sit back and build a formidable force rather than continue to chink away at my opponent 3 minutes in until I wear them out first. That's why on the rare RTS's I have boned up and played online I usually play on teams. That way, one of my teammates usually takes the role of rusher while I build the force for the late game play.

You should also remember that a lot of the people in this beta are some of the most serious players about starcraft, the level of play is probably going to drop when it releases. But also learning how to defend against cheese are probably going to be your 15 first games :(

" You should also remember that a lot of the people in this beta are some of the most serious players about starcraft, the level of play is probably going to drop when it releases. But also learning how to defend against cheese are probably going to be your 15 first games :( "

" I play RTS games waaaaaaay too slow for most online matches.  After getting my ass obliterated 4 times, I finally got an opponent in my last practice match that was like me, so I finally got to just sit back and turtle up, then pump out some huge units.  While the conflict between my legion of marines with 6 Thors and 2 Battlecruisers and his Ultralisks and other creepy crawlies was pretty awesome, there's way too much rushing and stuff in most matches for me to keep up.  Is there a way to play just against AI right now, or is that just gonna be in the final release? "

" Starcraft is a pretty fast paced game. Maybe too fast for some players. To each their own. That's why there are other games by other companies for other types of people. "