January: avoid first four to five days because crowds are often still Christmas size. Generally manageable crowds thereafter with some increase marathon weekend and days around MLK but even then it is not bad. It can be warm (day temps mid to high 70s, night temps mid to high 50s) or cold (day temps 40s to low 50s, night temps 20s) and sometimes both extremes in consecutive days.
Feb: Feb seems a little more steady with high 60s to mid 70s usually becoming the norm as the month progresses although you can still get a cold stretch. President's Day time (Sat before to Fri after) is usually very crowded but rest of Feb is manageable.
March: temps become more consistently in the upper 70s and steadily into the 80s as the month progresses although a cold day can happen once in a while. Early March is not too crowded but once you hit just before mid March you are firmly into the spring break crowds. Also week before and of Easter are the most crowded of the year next to Christmas week and thus if either of those are in March, you likely want to avoid.
As far as reservation difficulty, if you are talking about Jan 2013 through March 2013, you may have a difficult time with anything reserving this late other than SSR and possibly OKW or AKV (standard or savanna). If you are talking 2014, then at 11 months out you are virtually certain to get anything at your home resort other than possibly AKV concierge if AKV is your home. If reserving at 7 months out for that period you will likely find what you want unless you want AKV concierge or value, BLT standard, BWV grand villa, and possibly BCV or BWV standard or boardwalk view(although even those are open at times during that time period)