I started 4-5 years ago and once I got going I couldn't put the damn thing down. I've never taken a lesson, so I can't comment much on that but I have learned quite a bit myself pretty effectively.
For starters, expect to spend a few hundred on an acoustic. I feel if you cheap out on your first guitar just to see if you like playing, you'll inevitably hate it, as playing on a guitar with bad action [action is the height of the strings from the fret board] is pure agony. As someone else said, action can be adjusted but you shouldn't have to mess around with a new guitar, they should come set up from the factory.
As far as brand to get, there are lots of good ones. I highly recommend Seagull, Fender, Epiphone, Martin and Taylor. The latter two are more expensive, but you can find a new laminate top Martin for 300-400$. If I were to recommend one, I'd say Seagull. The action is great, the bodies are big so you get rich sound, and they have solid wood tops. That's probably the biggest determining factor you'll want to look for, when selecting an acoustic. Solid wood tops always sound better than laminate [however my laminate martin sounds great and gets more complements than most of my other guitars]. If you want a new guitar, I'd recommend going to a shop and telling the salesman you want a solid wood top, and go from there. If you don't mind a guitar with a little character, go to a pawnshop after doing a little research and you can likely stretch your budget.
You'll need some picks as well, get a few thinner jazz style, as well as some heavier gauge. They both play different and have totally different attack [attack is how aggressive the picked note sounds]. You should also go ahead and pick up a set of strings and a string winder, stringing it your first time is daunting but the sooner you learn the better. There are a ton of lessons online about how to string a guitar. Most, IMO, are not the proper way. When you are ready to string your guitar the first time, feel free to PM me and I'll walk you through it. I've literally never broken a string I've wrapped myself and I play very aggressively.
As far as teaching yourself, there are several ways to go about it. I use www.ultimate-guitar.com
to look up tabs for songs. Tabs are a bit confusing as they show which note to hit, but doesn't display rythym. You can download programs like Guitar Pro that play the tabs so you can see both notes and rythym. Learning tabs is an easy way to learn songs you're familiar with, but you won't learn much about music theory. Learning music theory is arguably less fun, but more rewarding in the end. This isn't to say you can't do both, but you'll likely lean closer to one. Youtube videos can be very helpful as well.
If I were to recommend where to start learning, after you learn basics like how to hold the pick, I'd say to start learning your 7 basic 'cowboy chords', and then to start picking up the blues. If you want to play any rock and roll or most modern music, you'll need to know basic blues shuffles. But, this is up to what kind of music you want to end up playing.
Remember the first couple weeks are rough, but once your past that it gets more and more enjoyable, exponentially.