This isn't your first year though it is Balu? What have the international guests done in the past? This is mine. Unbelievable! But since it is, I just recently had the AMA requirement presented to me adn didn't want anyone else to get caught unaware.
What have you done in the past?
Not having worked as a volunteer for registration, I can't say for sure, but I believe they do offer single day event registration options for getting an AMA number.
Also, I'm not an event manager, but have participated in them at my club in a support capacity. I know that most of our events are C or unrestricted events. I suspect FliteFest is the same. For those, it's available to all AMA members, and any affiiliated organizations such as MAAC (for Canada). For people outside of AMA and MAAC, I believe that's where the event based membership comes into play, which they call an Affiliate Membership.
Here's the text in the event managers guide:
2. Membership Applications for Affiliate Members
On current membership applications, there is a certain section for Affiliate
Members. To properly determine the eligibility of foreign participants to enter an
AMA sanctioned event, the EM must make sure these participants possess a valid
membership card from the aero club representing their country or an FAI Sporting
License. (The possession of an FAI Sporting License would indicate that the
participant has an aero club membership, but the reverse need not be true.)
If they have a valid membership with their aero club, they may apply to be an
Affiliate Member in AMA and participate the same day in a sanctioned event. The
Affiliate Membership provides liability insurance coverage for the foreign
member while he or she is flying in the United States, both for sport flying and for
sanctioned events, as long as the flying is done in compliance with the current
AMA Safety Code.
Current MAAC membership cards can be accepted for entry in place of AMA
cards. Be certain to identify the numbers as MAAC.