its not just bichons, most toy breed dogs are known for being "difficult" to housebreak, i think much of the problem is, many people dont realize with smaller dog comes smaller bladder, many toy breed pups take longer to develop to the point of holding its bladder 8 hours, the other problem is toy breeds are so small that they can get under tables and beds and when they squat to pee its not half as abvious as say a lab squatting to pee in the middle of your floor, i know when my 5lb pees you dont even realize shes squatting because shes already low to the ground.
they just require a little more frequency and patients is all.
chis are notorious for being difficult to housetrain, yet all 3 of ours are 100% reliable to a pee pad (and outside but during the winter they refuse to go out) and were trained and reliable very quickly!
every bichon ive ever met has been happy, peppy and outgoing.
its one of the few toy breds i personally think are usually ok around younger kids. (5+)