To find an inexpensive local party room, consider a church hall, museum or a reasonable hotel banquet room. Consider throwing the party on an off-peak day and time, such as a weekday or a Sunday afternoon.
Make the party reservation far in advance, and avoid a summer party, if possible. Have an idea of the attendance numbers to find the optimal space to suit your party's size. Call banquet halls to ask about discount packages and compare these with other room and vendor options. Some hall locations are more affordable than others, but if you want the party to be in a specific part of town, consider using a restaurant or community center.