While government entities can't restrict political speech on private property, homeowner associations are based on contractual agreements among owners to abide by common rules. Therefore, associations aren't bound by rules preventing governments from placing restrictions on political displays.
They are, however, governed by their state's law. In New Jersey, such bans are permitted. In the 2007 case of Committee for a Better Twin Rivers v. Twin Rivers Homeowners Assocication, the New Jersey Supreme Court held that associations could place reasonable limitations on political speech. Twin Rivers had limited signs to one per lawn and one per window and banned the posting of signs on utility poles and natural features within the community. The court found those limitations reasonable.
On the other hand, for example, since 2005 Texas law has prohibited associations from adopting or enforcing rules that prohibit owners from displaying political signs advertising a candidate or ballot initiative on their own property. The law covers the period from 90 days before an election to 10 days after. If a Texas association's governing documents don't ban political signs but only restrict how they're presented (in the ground or in a window) and their number, the association is probably on solid legal ground.
Washington also prevents associations from barring political speech. According to Washington statute, an association's governing documents can't prohibit the outdoor display of political yard signs by owners or residents on their own property before a primary or general election. However, Washington does allow reasonable regulations on the placement and manner of political sign displays.
There is no such protection in Florida. Remember that even if your documents allow your association to ban or regulate political signs, you may run into difficulties enforcing your rules. A McCain for President sign plainly fits the definition of a political sign, but it's arguable whether a peace sign is political. Case in point: In December 2006, a homeowners association in Pagosa Springs, Colo., asked a resident to remove a wreath shaped like a peace sign from her property. The association backed down after negative publicity, but the example highlights the fact that it's hard to decipher what signs even fit the definition of political.