How well could I do in a street fight?

BJJ is a sport based style. It wouldn't do well in a street fight. In a street fight you're likely to be either outnumbered or in an area with debris on the ground. Neither situation is good for BJJ. If you managed to get in a street fight on a grassy meadow against one person, you'd do good, but that rarely happens in real life, especially if you're trying to avoid a fight like any real martial artist would.