Can we run a PDGA league even though we have very few PDGA members in our area?

Yes. Some TDs may either want to or be required to sanction their league for the PDGA insurance coverage. It takes at least 5 PDGA members with established ratings over 799 to produce Preview (unofficial) Ratings online each week. However, even if your league has fewer than 5 players with established ratings some or most weeks, the PDGA will use an alternate method to generate official ratings for the current and hopefully new PDGA members in your league once your final league results are submitted.