While I agree with you that WR is a big need, they will not take two in the first 2-3 rounds... Not to say they won't draft two WRs, one early, one late... but we have many other needs and a guy named Lee Evans to re-sign...
If the Bills stay put and draft at 11, there are 4 needs they should address (WR, DL, LB, CB)... and depending on who falls, it may not be at WR (a deep position this year that can still yield a starter in the 2nd or 3rd)...
They could draft DL... IF guys like Sedrick Ellis or Vernon Gholston drop (doubtful but I've seen stranger things) or maybe Phillip Merling... Again, DL is a good option, but a little less likely because the DTs probably won't drop (Dorsey & Ellis) and the Bills already have a lot of money invested in DE....
They could take a LB... Crowell is a UFA next year and Ellison and Digiorgio are RFAs... Could we re-sign those guys? Sure... easier when they're RFAs, but having a replacement as well as insurance in case Mitchell isn't everything we need on the weakside gives the Bills something to fall back on... A guy like Keith Rivers could be a tempting pick....
Then there is CB... People have argued that the cover-2 does not put as much emphasis on the back-end, instead using zone-coverage, which argues that CB can be taken later... I for one think a great corner is a great corner.... period. The scheme is secondary to talent... and there are a slew of talented CBs available that the Bills can get.... not to mention we are thin at CB right now....
WR would seem to be the most obvious first choice... At #11 the Bills would most likely have their pick of whoever they see as the most talented and best fit in the offense... It provides insurance if Evans does not re-sign and gives Edwards a tall, jump-ball target... But again, the WR class is deep, the Bills have other needs, and two WRs in rounds 1-3 is a bit too luxurious... especially for a practical team like Buffalo...
Another choice for Buffalo might be to trade down... which would open the possibilities up to other positions like TE, OL, FB, etc. I don't believe trading down is as easy as a lot of fans think it is (people seem to think that's the sure-fire option every year, without fail), but if they could pull off a negotiation, it's a good choice...
I actually believe the Bills will have many options where they sit and a very hard choice... and depending on who falls, they could go a lot of ways... If they have proven anything lately, it is that their choices are very much unpredictable!