Is there any possible way to wait until you get your boots to buy the bindings, or are they used and you only have one option type of thing? If possible I would wait to see what size boot you wear, but the L cartel's are made for size 10+ so you should be fine. You can always ask for some large cartel's while you're buying your boots and try whatever size fits right in the L cartels.
I am not sure about the size of the binding, but it is highly unlikely that if you wear a size 11 shoe that the boot is going to be a 9.5 or even a 10. I wear size 10.5 to 11 shoe and I wear size 11 boots.
I could be incorrect here but, i think the smaller binding is for 9.5 and below and the larger one is for 10 and above. Maybe someone else can verify this.
A lot of it depends on the boot you get. I HIGHLY doubt you will wear anything under a 10.5 with a shoe size of 11. I have 10.5 boots with Cartels and they work out well. I have them on the MEDIUM settings for the cartels so it would probably drop down a size or two on boots. I'd first try a local shop but you should be fine with L cartels and 10 boot. I doubt you'll wear a 10 but go to a place and try on boots!
like everyone else has said, if your a size 11 shoe, your boot should be that much different. i think bindings have a little bit of play in their sizing. i actually fit my size 12 salomon boots into large ride binding, but their sizing recommendations on the bindings say that i should have xl bindings.
Thanks for all the replys. The reason I am asking is that I won these binding a couple weeks ago. I have never snowboarded, but always wanted to. So, I looked at the sizing and picked the Large (10+) based on my shoe size. Later, I found out that boot size can be a size or 2 small than my shoe size, so I started to panic a bit.
Looks to be a none issue. Thanks again for the info. I am going look for boots this weekend and will probably take my bindings with me to make sure they work together.