Read the rest of this document before you purchase seed. Here is a snippet:

From UF:

Improved bermudagrasses require high levels of maintenance. They have poor tolerance to many insect, disease, and nematode pests, which limits their use in home lawn sites. They grow very aggressively from stolons (aboveground stems) and rhizomes (belowground stems) and can rapidly invade flower and landscape beds. This aggressive growth also fosters thatch buildup. Bermudagrasses generally have poor to medium cold tolerance and relatively poor shade tolerance. Since bermudagrass performs best with higher levels of fertilizers and chemicals than other Florida lawngrasses, a professional lawn care company may best handle maintenance of this species.

Bermudagrasses are established vegetatively by planting sprigs, sod, or plugs. Each of these methods can be equally successful if the site is properly prepared before planting and if correct establishment practices are followed. For detailed information on lawn establishment, refer to the Edis publication LH013, "Establishing Your Florida Lawn." The best time to plant bermudagrass is when plants are actively growing, normally April through September.

Here is a link that might be useful: Bermudagrass for Florida Lawns