Hibiscus are a number one in my sulcatas book! Both the leaves and the flowers are very good for them.
Grasses should consist of a major part of their diet. Let them graze as much as possible.
There are some good sites out there with nutritional info you can trust. sulcata-station.org is a great one.

Rich
-----
bigdnutz
1.2 Suriname Boa
1.0 Venezuelan Boa