Noooooo don't do the Glock. And def not the nine.
First of all, the safe action trigger isn't all that safe. Any pistol that is to be used for sd/personal protection should be carried condition one, or "cocked and locked" if you prefer. All that stops the Glock from being fired is that little trigger piece being pulled with the trigger. There are too many stories of LEO's getting out of their car and their jackets pulling the "safe action" trigger....
Second... Glocks do not have a fully supported chamber. A term has been coined in the gun community that is pretty self explanatory---"Glock kaboom," where the casing ruptures at the place where it's unsupported. It's rare, but happens. Why take the chance in a tool that has to work perfectly...every time.
Third... Grip angle. On Glocks, grip angle is angled down from a more traditional grip such as say 1911 style. Your knuckles actually point more downward and a great number of shooters find it not as natural. And when you are quick drawing and must instantly find your POA it should be where you point, not where you aim.
Fourth... Ughhhh 9mm.
---Power
A 9mm might be okkk with a +P TAP/HydraShock type cartridge, but in a SD type situation, you want something that has the greatest chance of incapacitating the perp in the fewest rounds possible. You can get fairly small .40's.... and .45's for that matter. The only thing 9mm has going for it is mag capacity. But if you need more than 5-7 rounds to down someone, or a few someones you shouldn't have a gun in the first place.
Now for recommendations.
Obviously if price weren't an issue, and I needed a purely offensive sidearm, it would be a service size USP or a Sig 226 in .45ACP, but I don't have $1000 nor a use for such a weapon right now as I'm sure you don't.
Under $600 you say? Safe you say? Light you say?
Springfield XD is you answer.
Comes in 9mm(booo), .40S&W, .45ACP, and other less popular chamberings as well. It's polymer framed. It has a 1911 style grip angle. It has a fully supported chamber. It costs on average $100 less than a comparable Glock. It has survived publicized torture tests. It has an integral light rail and ambidextrous mag release. And it feels better and fits my hand better than any other .45 I've ever put my hands on. XD's come in the 3"barreled sub-compact, the 4" barreled service model, and the 5" barreled tactical model. The .45ACP XD comes in service, tactical and the new .45ACP compact which has a 4"service barrel but has a shortened grip and 10rd magazine and an extended 14rd mag. The. .40S&W subcompact is very concealable. I (in 1 month) am going to conceal carry my .45 compact. which is very do-able, even in .45ACP.
Springfield Armory XD safety features--It has a trigger safety like the glock but is more comfortable as it's angle is more flush with the trigger. It also has a grip saftey which must be fully depressed in order to pull the trigger and/or for the weapon to fire. Also, it has both a loaded chamber indicator and cocked indicator that can both be felt as well as seen from firing position. It's almost impossible to fire the weapon accidentally without one's hands gripping it properly, but can still be carried "condition one."
If that however, is still too big or if your looking for a small "purse/pocket gun," look into the Keltec P-3AT. It is VERY small. I think it even comes with a "pocket clip" similar to a pocket knife clip. It's chambered in .380 auto which is a small round, but if you're really trying to go concealed..... If you used Hornady TAP/Federal HydraShock cartridges, if would more than likely get the job done in an emergency. This is more of a I'm being rapped-point-blank-range-fire-the-entire-magazine-into-the-guy type weapon. I'll probably pick up one of these for a CCW for those HOT New Orleans summer days.
I hate that damn system. Only real fault I have with mine. External safeties are ftw.