I've started to learn the bass guitar and am looking into getting my own instrument. Was thinking of getting an acoustic bass - would be great for jamming in all situations and lighter. Have heard that they tend to be rather quiet though. Any comments??

An acoustic bass is good where you don't have a place to plug in and don't need amplification. But if I had a choice, I would choose the bass guitar because it is much easier to carry and transport. There is hardly ever a time that you won't have a place to get electricity even if you have to use an extension cord. Now the amp can be hard to handle unless you get a smaller one. You don't really need 800 watts to be heard. 50 or 60 watts would be plenty unless you are in a rock band full of those 800 watt amps. I use a 100 watt amp and only turn it up to arouns 2 on a scale from 0 to 10. I play in a praise band at church with others that are amplified and they are always asking me to turn it down.
You have to consider where and who you are going to be playing with to make that decision and what are your needs now and in thte future.
I hope that helps.

I have an acoustic bass guitar, the only reason I have it is for when I do street gigs with my guitarist, even when I do those I sometimes bring my electric bass and just use a mini amp. I would say sure get one if you are going to be playing with just acoustic guitars and a singer, or if you get an acoustic electric then you could always just plug it in.
Unplugged acoustic basses are very quiet, I would recomend if you do play unplugged then use a pick, they make the bass louder.