The manitoba social

It's been awhile since I've planned one of these. Our social is in April. When does one start putting out letters to local business and other businesses? For instance some places will not be opened in April for the season yet so should I send the letters in now before the end of the season in hopes they date them for next year? I have gone on the Manitoba Socials Page and written down the good ones I know that work. Does anyone have any more idea for social prises or suggestions of what worked well for you or other social you went to?