I grew up in Hawaii and go back to visit regularly, the fabric stores that is...
Fabric Mart actually has three locations on Oahu & one on Maui. I agree with the earlier comment; the Aiea store is a little hard to find and the last time I went there it was the least organized of the 3 Oahu stores. There is also one on Kalakaua Ave in Honolulu & one in Kaneohe just after you come over the mountains. Plan to spend lots of time there - the bolts are in huge stacks to the ceiling and it takes a while to work your way through it. In addition to 50/50 Hawaiian prints in rolls (around $4-5/yd) they also have tons of 100% cotton for quilting. (also a great price) This is where I used to get all my old Rose & Hubble / William Morris fabrics. Fabric Mart has their own parking lot - worth gold at the Honolulu store.
I also love Kaimuki Dry Goods - it's been there as long as I can rememeber and has a beautiful selection of Asian fabrics as well as other Hawaiian, quilting & formal apparel fabrics. It is not cheap but not out of line from what you pay in a quality quilting store. It is set back behind another building (a bank, I think...) off the main street - Waialae Ave though the address is technically on 10th Ave. Beautiful fabrics!
I have also gone downtown, near Chinatown to a couple of fabric places that remind me of the LA garment district only on a much smaller scale. They were much more about apparel fabric, messy and to me not worth the hassle of parking and walking around to find the small hole-in-the-wall shops. I don't bother with them anymore unless I'm looking for a Hawaiian apparel knit or formal fabrics for cheap - then I might check in a couple of those shops. At the time I used to occasionally go there I wasn't quilting so I never looked for those fabrics there but my memory is that's not what they carry.
There are also many small quilt shops to check out though I am only familiar with the ones on Maui so can't give specifics. They will probably have patterns that are new to you with Hawaiian symbols - turtles and breadfruit, etc as well as traditional appliqued Hawaiian quilting. Enjoy! And remember to bring an extra suitcase
Though even that didn't save me from having to pay for overweight luggage due to all my fabric on the last trip... might be worth mailing some home to yourself too. Shannon