I would like to speak Quenya as my main language while residing in Falas. Is it possible to do that?
Yes and no. Falas falls under the rule of Elu Thingol of Doriath and he has decreed that Quenya will be spoken in his realm *only* under penalty of banishment. Therefore, if you wish to have Quenya as a base language in Falas, you must obviously be very careful about speaking it and most (if not all) Elves would strictly follow this decree of Elu Thingol anyway.