I guess I will bring it in. It is very important to me.
You need to know which one you have. Unfortunately, garden centers, nurseries and home improvement centers lump all hibiscus together.
If your hibiscus has glossy deep green leaves, 3-6" flowers of red, pink, orange, yellow, double or single flowers, it is probably a TROPICAL hibiscus. While many common garden varieties have the 3-6" blooms, many of the hybrid varieties of tropical hibiscus can have blooms around 10" in diameter under ideal conditions.
Another way to check is if the flowers are salmon, peach, orange, or yellow, or double flowered, then you probably have a TROPICAL hibiscus. Hardy hibiscus do not come in these colors or in doubles! Many tropical hibiscus flowers have more than one color in a bloom either in bands or as spots.
If your hibiscus has dull medium green heart shaped leaves, dinner plate sized white, pink or red flowers with HUGE, bomb shaped buds (2-4" in length!), it is a perennial, hardy hibiscus.
Hardy hibiscus need very little care over the winter, they are root hardy to about zone 5 with no protection. They die to the ground each year.
If you have a tropical hibiscus, remember it is a TROPICAL. They will not tolerate more than a night or two of light freezes. Even one hard freeze (below 25) could kill the plant. These plants are native to sunny, warm and usually humid tropical places.
They detest cold, rainy weather and cold, wet soil. They will not reliably survive outdoors north of zone 9. In all other areas, it may be a good idea to bring them indoors BEFORE temps regularly drop below 40-45 F at night to avoid any damage.
Treating your tropical hibiscus correctly will give you years of enjoyment. But remember, they are not immortal! Some are spent after 4 or 5 years in a pot and should be tossed away at this point. Try some of the many and never ending new hybrids being developed!