I bought hibiscus plants from Walmart yesterday. Are they perrenials?

Tropical hibiscus plants are either brought indoors during cold weather or are treated as annuals, because of their sensitivity to the cold. Perennial hibiscus (Hibiscus spp.) are known to be cold hardy, but will still die down to the ground in all but the warmest U.S. Department of Agriculture plant hardiness zones.

Yes, they are perennial, and they are gorgeous! Here's a video that you may like. https://www.youtube.com/watch?v=ICYMjyQ7PMM

Yes! Make sure you water well when you plant them and always keep them on the damp/wet side thereafter.

most will come back each year and will grow larger/fuller each year.

Hello Virginia, Yes, hibiscus are perennial :)

http://homeguides.sfgate.com/care-perennial-hibiscus-tree-year-round-42113.html