Lit in the modern vernacular means not only "intoxicated" (or "lit up") but has come to be a positive modifier which occupies roughly the same semantic space occupied over the years by such terms as cool and groovy, and swingin(g).
This very day in the New York Times, the "Quotation of the Day" is:
If you use the expression as in your question, though, you will tell your listener that you (the plural you) intend to become intoxicated this weekend. If you want to communicate instead that the party will be enjoyable, you might express it as:
"The party this weekend is going to be lit."