I agree with what Sara and Tuss said. I'd want a breeder who is familiar with, and regularly does temperament testing. Besides a healthy, well conformed, sturdy individual from fully health tested lines, (and preferrably with performance dogs in the family!) you also want an individual with strong play drive, food motivated and people oriented. Temperament testing can give you clues to all of that.
I was specifically looking for a performance dog when I got Kodi. I not only looked for a breeder who had dogs fitting the above criteria, but I also took a trainer with me to assess the puppies and put her "seal odf approval" on the pup I got. Her only admonishment was that if she told me none of the puppies were the "right" pone for me, I had to PROMISE to leave without a puppy... She said too many people asked her to help find the right dog, than fell for a "cute face" in spite of her warnings.
It was really interesting seeing her temperament test the puppies. All of the, with sweet, and all scored extremely well in terms of "pet qualities". But among the three, there were subtle differences to be seen. One was VERY bold and adventurous with great play drive, but had a bit of an independent streak... He was not as "people oriented". Another was a bit distractable (we started referring to him as the "ADD pup"
) but was the MOST food motivated of the three. The third was also pretty brave and had strong play drive (thou not to the extent of the first) but was VERY people oriented. A quiet "Pup, pup, pup!" was enough for him to break off playing with his sibs and come bounding into your lap!
The trainer explained to me that all 3 of these puppies were eminently trainable, but that you would probably need slightly different approaches for each. The first would probably challenge authority a bit more, but had the high drive you want in an agility dog, and the independence to willingly work away from the handler. The second, though distractable, still had a good "hook" in that he was so food motivated. The third, though not as high drive as the first, had the advantage of innately WANTING to be a "people pleaser". After talking about all 3 pups, the fact that I wanted to do obedience as well as agility and that that "people pleasing" attitude would go a long way toward winning over my less-than-enthusiastic husband i went with the 3rd pup.
Kodi has been everything I wanted him to be and more. He competes successfully in formal obedience, rally and agility. He snuggles with us at home and goes for long, off-leash walks in the woods with us. He's a fantastic competitor AND the perfect pet! He is a touch on the sensitive side, and I have to be very careful to be very encouraging in agility, and not EVER let him think he's made a mistake. (as you no doubt know since you are already doing agility, most "mistakes" are handler errors anyway!
). But i can't even show frustration with myself, or he is liable to shut down. So we are taking it slow in agility, and building his confidence without letting him get stressed. He's got his first two novice standard legs in two trials, so he IS doing well there, in spite of a novice handler!!!. OTOH, he is BRILLIANT in the obedience and rally rings, where he is more sure of himself.
Since you seem to have a lot of Havanese competing in your area (we don't around here... Kodi is the only one most of the time in obedience and rally, and there are just a handful who do agility) I'd do what Sara suggested and talk to the people at trials who have dogs you like. Ask who their breeders are, then talk to the breeders and tell them what you are looking for. I can highly recommend my breeder, but it's a long way for you, coming from CA. OTOH, I do know they'e sold puppies to CA, so it's not out of the question.
I've already told my breeder to be on the lookout for the "right" puppy for me in the next couple of years. Just like not every litter is going to have Grand Champion potential puppies, not every litter is going to have a top athlete who also has the perfect mind. I'd rather wait another couple of years for a puppy... Ideally, I'd like Kodi to be working on his UD in obedience, and at least at open in agility before starting another rug rat!
. But if she called tomorrow (I'm safe there... She won't have any more puppies until spring!
) and said she had the perfect puppy, I'd be lobbying my DH HARD to change the time line. To me, the perfect dog is more important than the perfect timing!