Welcome here. Always summer in Naples? Wish I was there now. Grew up, just north of you in Ft. Myers.Gotta love that climate.
Just received in the mail a letter from a heating and air company giving a discount on a system checkup. It's probably a slow time for them. I'm sure everyone else in the neighborhood got the same letter. 20% off their normal price @150 for a 30 point check. Additional charges apply if they have to cut open any duct.
You might also think about door hangers or flyers at a shopping mall parking lot.
Maybe get some refrigerator magnets that look like your business card. Leave them on the equipment where it can be seen when anyone checks filters, etc.
Good luck with your business.