Sorry you haven’t received your form! We are a state committee promoting the Census 2010. We are not the U.S. Census Bureau, so can’t help you directly – but you can visit this website: http://2010.census.gov/2010census/ for assistance.
There is a box on the page that you can click on “Find my Questionnaire Assistance Center”. You will then get a new page where you can enter your city/state or zip code, and it will bring up a map of the Questionnaire Assistance Centers in your area, and by “mousing over” the map locations, you can get phone numbers and hours, etc. One of the USCB people staffing those centers should be able to help you!
As to the timing – the USCB would like the forms returned as soon as possible, but they don’t start their door-to-door follow up with census workers until late April/early May, so you’re still within schedule for a while longer!