It never hurts to ask a breeder how their pairings are going - by now they should have a good idea of which snakes they can expect offspring from. So an initial inquiry with a breeder you know is planning to be at the expo, plus a followup around July may help. I'd stay on top of it if I were you; the dwarf varieties seem to sell fast. I know Vin Russo told me that when he announces his Tarahumara babies they are usually sold out in 15 minutes. I have faith you will get connected with the right breeder and the right snake, though!
Breeders obviously don't want to be peppered with questions from window shoppers, but I've found they respond really positively to a polite, serious, specific inquiry. One other thing to consider in terms of your planning is the possibility that COVID19 restrictions may impact the expo. My regional expo is also at the end of September and there is at least preliminary discussion of that possibility. Don't despair if you end up not being able to make face-to-face contact with a breeder. Michael made himself very much available to me by email and phone, and we've had multiple conversations about how things are going with these babies. You'll find that a good breeder will welcome knowing how things are going with their snakes, and they will be there to offer info and support.
I'm so glad you have enjoyed the Tarahumara posts I've made so far. I really love these little guys and am delighted to inflict more photos and stories about them on anyone who will listen. I'm also a huge fan of the spotted/stimson's/children's pythons - I have two - and agree that you might really enjoy having one of those as well. But I understand the enchantment with the Dwarf Boas, and look forward to hearing about how things go with your search.