Oil-based exterior paint is highly recommended when palm sap and residue are a problem. Although less convenient to use than latex products, oil-based paints have better adhesion and are more stain resistant. Latex paints are more vulnerable to damage from tree enzymes. Enzymes act like solvents, dissolving certain elements in paint and weakening them. Latex paint can blister and pull away when sap is scraped off.
Flat-finish paint is the most popular paint for home exteriors but also the most easily damaged. Paints with a shiny finish have a smoother surface that resists dirt and sap better than flat paints. Sun glare, however, can make a home with a glossy finish look garish. Using a satin-finish paint is a good compromise. Use satin-finish paint for most of your home and semi-gloss paint for doors and trim.
Start a paint job with a good exterior primer to improve adhesion and resist stains. Where humidity conditions are challenging, upgrade to an industrial-maintenance coating that can be used as a primer or as a protective clear coat. An acrylic primer and sealer gives you a broad range of colors from which to choose, as well as durability.
Additives offer a way you can have the easy cleanup of latex paint and get the tough finish you want. Check the professional paint supplies section of your local paint or home store for stain-resistant additives and sealers. Mixing the right additive into your paint will improve adhesion and prolong the life of the finish.