Portugal has some excellent white wines, but not so many are exported with the export market favoring vinho verde. Esporao is one of the larger producers in the Alentejo and orients their wines toward the export market. In fact I believe they have a foreign winemaker. Another Portuguese white that is readily available is the Quinta da Romeira Arinto, which is probably not as complex as the Esporao, but I think reflects the whites sold in Portugal and is quite drinkable. Locally I have seen the 2003 and 2004, but I believe the 2005 is already available.
There was another Portuguese white which was my absolute favorite, but I have not been able to find it in the past year. I need to scope out a few other establishments to see if I can find it and if so I will post.
PS When I visited Hawaii we were striking out as far as wine, until I happened into the Long's Drug in Kukui Grove Shopping Center. They had all sorts of interesting wines and some great values on Californian wines (ridge single vinyard bottles under $25). We ended up doing a lot of corkage fees, room service, and picnics for the rest of the trip. Of all the bottles we bought, we only had one corked bottle.
I'll look for the Quinta da Romeira Arinto. If I don't find it at Long's, I will look when I am on the mainland next. (The Longs you mention is where I often buy my wine. The selection is indeed pretty good, but I have had a surprising number of bottles from there that were bad. I think the quality control is not good and they get overheated while being shipped here.)