Probably the most experienced guide service in the East Cape area is Gary Graham. He has an archived list of reports here:
nevadacaster is right, that your best bet that time of year is the Sierra Mackeral. Think spanish, but twice the size...good 8 wt fish, they school, so if you catch one, you should be on a bunch.
You're right that you are unlikely to get Dorado or Billfish at that time. I've fished of the beach at the East Cape area once in February, once in March and once in May. May was by far the best, but I was able to come up with some Jacks in both Feb and March, as well as different members of the snapper family.
I haver used Gary Graham's book, and a rental VW bug to find some nice remote beaches with some great schools of big jacks herding bait right onto the beach at your feet. 10wt probably best.
Hope this helps...have a great time.