I'm getting married this weekend. When I file taxes can I still file as single since I wouldn't even be married for a month?

No, you are not single, the filing status is what you are, on the last day of the year.

If you marry one day before the end of the year, you would file as married

Besides, filing a joint return will probably result in a higher refund, though you should model it as a joint return and two Married Filing Separately to see which is best for you and your spouse.