J.
I've lived in Oak Park for 9 years now. We live in south oak park not far from the pool. It's a friendly, family neighborhood and I really love it here. We know our neighbors and everyone watches out for one another. Love the community and walkability - it is my dream neighborhood in many ways.
But it is an urban area, so you have to like that sort of dense living, and I do. I haven't heard anything about gang activity through the grapevine, but there are random crimes and property crime is not uncommon (bike thefts, that kind of thing.) I feel like I know the neighborhoods pretty well and I personally wouldn't say any particular area is a bad area. Most people would probably avoid the first block near Austin, but I don't know that there is any specific reason (other than it's closer to the city.) I think all of our grade schools and both middle-schools are very good.
If you can, meet some neighbors and visit the block at night and at rush hour to see what traffic is like. Good luck in your house hunt! If you aren't working with a local realtor, I'd definitely try to get to some open houses and at least have some conversations with someone who knows the local market well.
ETA to add in response to the response from Diane that I live in South Oak Park, and the impression I have is that we are having an explosion of kids in this area! Our block had just 3 families with children under 12 when we moved in - now there are more than 30. My friends who live in the Beye school district feel like their neighborhood tilts more to older people. Lincoln and Irving schools are both having to add classes and teachers the past couple of years. But if being around young kids is important to you, this is a good time of year - just walk around on a nice day at about 5:00 and see who's out.