Notify the appropriate authorities that you do not wish to be exposed to pesticides as a result of drift, runoff, or vaporisation. You should inform them of any limitations you have, such as chemical sensitivities, allergies, asthma, or a weakened immune system, which could prevent you from accessing your own property or public facilities due to their spraying.
Some towns, counties, or states require a recognisable sign, which you must register for at the relevant office or online, as well as a "no spray" request. Notifying the relevant person may be more difficult than it appears.
Of course, knowing ahead of time can help you prevent unnecessary exposures. When notice is not given, drift might become more acute. In certain situations, or in all cases, some municipalities have legislation requiring warning of upcoming pesticide applications. Some states have enacted legislation prohibiting local governments from enacting similar ordinances.
Get the copy of the safety data sheet (SDS) and label of the chemicals to be sprayed. If it is not possible to vacant the area stay indoors during the spraying and keep your windows closed. This might get tricky.