I want to buy a bike
 

But I don't know anything about bikes. I just want to ride it to BJJ and work.

Can you recommend me a decent bike?

To a bike geek that is totally a loaded question, darn close to a troll. Are you looking to buy a new bike or pick one up on craigslist? If used any modern mountain bike would probably work. If you pick up a bicycling magazine there is usually a section in the back where they reccomend bikes for people that might give you some ideas about what to look at.

I'm looking to buy new or used. I would be riding it a max 7 miles or so at a time, nothing spectacular.

Would Wal-Mart be an ok place to buy one?

I don't want to end up getting a crappy bike where the brakes break within a couple months or something.

no. go to reputable bike shop, get sized, figure out what feels comfortable in terms of style, road, cross, mountain, single speed etc..then buy the most expensive helmet they sell and look for the bike you chose on craigslist.

Been through a few Walmart Specials. However, both of them ended up getting stolen.

They were ok, but over a few months some things get loose that never seem to be able to get tightened down. Out of the store, they typically ride fine.

If you can find a tour bike on CL, I would do so. You will cover a lot more ground on them than a Mtn bike which is nice, even in wind. Mtn bike suck in the wind.

Shimano components are always nice, imo.

get a cheap "track" bike (single speed)... no gears but with a front brake... and then just take some black or whatever color vinyl and cover anything that looks fancy..

should be able to do it for like 500-600 bucks and you get a super light road bike

You don't even have to necessarily go to a "reputable bike shop." A sporting goods store can provide you with an excellent selection of bicycles. Modells (On the East Coast - my sister lives there) and Dick's Sporting Goods are great options for buying a bike. Of course, if you want the advice of a professional biker (non-Harley, of course hee hee), then sure, DO go to a bike shop. Of course, not every town has a bike shop and it can cost a pretty penny. Good luck!

I've been through a bunch of bikes over the years including both mountain bikes and road bikes and in my opinion if you are after a run around bike your best bet is to get something like an entry level mountain bike from one of the big manufacturers like Giant.

Throw a set of 1.5" slicks on it and you'll have a reliable bike for day to day.

If you think that you'll end up doing a more riding it's worth upgrading a couple of models up the range to get better components but otherwise just spend as much money as you can afford on getting a good set of lights and a good helmet. I've had my life saved by a helmet on two occasions and again i'd go with something from a big manufacturer like MET or Giro (the most important factor being a snug fit)

As far as getting a bargain I've bought $3500 bikes for $1500 on ebay and had to sell a $3000 mountain bike for $975. In both cases the bikes had seen little use and the bike i bought for $1500 went on to do several years of weekly rides without problems.

As I recall, this thread had lots of good info on bikes in general: http://performancemenu.com/forum/sho...ighlight=bikes
May be helpful to you, or not.

Full face helmet FTW.