I've just finished restoring the forests of Arcadia, and I've realized that I've only seen one Bouncer so far (the first one that you fight). Is this the same for everyone? 

You'll find them again in the Fort Frolic and Haphaestus levels. You should get to Fort Frolic soon.

Hmm, I felt like I had run into a few other Bouncers by that time.  Interesting.
I much prefer fighting Bouncers, though.  Rosies fuck me up with their damn rivet guns.

man, I hate rosie's, bouncers are awesome, you'll find a lot in haphaestus.

Have just beaten the game today, and I have to say, Bouncers are definitely more fun to fight.

Yeah, I prefer the Bouncers to the Rosies as well.

The Rosies are alot easier to beat  IMO, they move around less and you just need to move around alot to avoid getting hit by them. That is wierd though that you've only encountered the bouncer, could it be the difficulty setting you have it on? 

Also, if you kill all the big Daddies on a certain level and you need them for research and achievements/trophies then all you have to do is use the bathysphere to go to another level, then just return to the other level and you'll have new big daddies there to research. 

bouncers are harder but way more fun to fight rosies are just kind of guys with lots of health

It seemed like Bouncers were kind of rare for me too, I was playing on the normal difficulty so I don't think it was that.  Maybe it is just kind of random.