What level are you by the time you get to Blight Town?

Usually about 30-50

I'm usually more along the lines of 30-40, but occasionaly I'll be be something like level 45 if I've done something like make a Darkwraith build since I have all the Souls from the Four Kings and Sif.

11-20, but around 30 is probably the norm...or at least it used to be.

Usually level 4 or starting level.

usually around sl 15, I use all my souls to upgrade all my gear first instead of leveling up.

Usually 16, unless if I'm in a hurry to make a build.

I'm starting level during my first foray into blight town. I head down there as one of the very first things i do, strictly for the loot and to get to the great hollow to join the path of the dragon covenant. I'm usually somewhere around level 20 by the time i kill Quelaag. Actually i'm usually around level 20 by the time i've done everything possible before killing the gargoyles.

I can't vote
It depends on build, weapons for me. Today I played solo with quelaag fury at sl 12 with my mage shooting soul magic. If I solo with nothing but a +5 halberd I could be anywhere from sl 15 to 30. If I'm playing co op, it depends on what my partner is. If I had to choose, I would say 20 to 30 mostly.

I'm usually in the 20s by Blighttown, very rarely above 30. I have a level 30 darkwraith which I also use for co-op and I get loads of action there as both an invader and white phantom with that build!