Either way though I think the next time I'm sparring I'm going to ask my friend to try to emulate your typical street thug attack and see how I react to it. I figure if I ever have to defend myself that is the most likely scenario and so that's the one for which I want to be prepared.
This is a great idea! Another scenario you may find useful is to get together with two or three training partners. Everyone gears up, and the fight starts with you walking past one of them. Then one (or more - you won't know) will move into an unprovoked attack. The attack can (and should) look different each time your run the scenario - it could begin with words and escalate to shoving and fighting, it could begin with an innocent question ("do you have the time?") and then move into the attack.
The key is that you don't know in advance how many people you will be dealing with (this is something they will work out among themselves and you will not be part of the conversation). It could be an attack by one person, that escalates into a two on one or three on one....or it could just stay one on one...or it could be multiple attackers versus you from the start. Also, some of them may be carrying knives or other weapons. Again - you won't know.
One important thing to work out in advance is that everyone is clear what you are fighting for, and when the drill ends. When my teacher and I train drills like this, we fight to get away. The drill ends when the fighter either gets away, clearly can't get away, or is "killed."
Train hard and be safe,