pilsner / lager temps - getting away w/ something

My understanding is ideally these would ferment at around 50 degrees through FG, then much colder, maybe in a 2ndary, mid 30s for another week.

I can hit the 50s no prob; that is my fridge.

How much can I get away with colder than that?

I'm in Chicago... difference between night and day is dramatic but we are approaching the point where it'll definitely hit 30s soon. Could I dump this in a bin outside surrounded with water to even out the day/night temp swings?

Or is this better avoided entirely? (should I stick with ales etc for now?)

Those of you who brew with these specific temps, how do you do it? Does everyone have a separate fridge they can control that specifically? Is there any easier but fairly reliable way around it?

Temperature control is rather important to bottom fermenting (lager/pilsner) yeasts. Most of them like the low to mid 40 temp range. If you let the temp fluctuate, it's going to wreak havoc on your beer. On thing you may think about to control your temps is making a fermentation chamber. There are several in the DIY section.

I'm on the NW side of the city and have an unheated yet insulated back porch. I found my temps get to about 5-10 degrees higher than the outside temp. I made a simple box out of 1 inch pink styrofoam to keep the temps relatively stable. I'll be putting a 6 gal batch of Kolsch in there tomorrow and monitor the temps for the next several days.

For primary 50's are perfect. For secondary/lagering temp is less important. Near freezing (even just a bit below) is best but in time higher temps should work out fine. Lower temp will drop the proteins out faster.