Hi- We're looking to spend a few days in Hilton Head and had some questions. We'd like to stay at the Westin Hotel (port royal plantation) but would like to leave the resort for dinners etc. Is a car needed or are there taxis? Can we bike to South Beach?
Any suggestions/advice would be greatly appreciated. Thanks!!

You are better with a car.
Taxis are few and far between on HHI.

Bike paths all the way to South Beach, but it's a long way

You need a car in Hilton Head. Go somewhere/anwhere else for a better beach experience.

Westin to South Beach is 12 miles one way.
HHI has great bike riding, beach and paths. Be sure and do some bike trips. Typically you can't leave your plantation on a bike.

The statement "typically you can't leave your plantation .. bike" needs clarification.
The island has many trails that are not within plantations.

As to Sea Pines, day visitors must purchase a pass. ($6 per vehicle, plus $1 per bike carried on the vehicle). To my knowledge there is no "bicycle-only" access through the gates. I know some people access the beach at S.Forest walkway near Alder Ln., then ride the beach and come in through SP Beach Club -- not a great idea for multiple reasons. From your location, a lengthy ride, and definitely not one to attempt after sunset.

There are miles of trails outside of the plantations to enjoy... far more than you could cover in a week. Please see the link below:
http://www.hiltonheadislandsc.gov/Island/pathway.html

As to restaurants outside Port Royal -- closest I think would be those in Pineland Station. We enjoy Il Carpaccio, but I've read good reviews on Le Bistro & Dye Gullah.
http://www.pinelandstationmall.com/

I agree with the previous posters who say you need a car to enjoy your island experience. If you are arriving by air, it would probably be cheaper to rent for the duration rather than rely on taxis.