Ubud was always a hot spot for backpackers and people looking for inspiration in their lives. In recent years, however, it has become a hot spot for many yuppies and upper class individuals. Because of this, Ubud is generally packed year-round. No matter when you visit, there will be a lot of tourists. To avoid extreme heat, you might not want to come during the summer. Although it is generally always hot in Bali, summer can get extreme highs, which can really bother some of the tourists. There seems to be more rainfall generally in Bali in the spring, but this is also the time when a great number of travelers arrive. During spring break for college students, a lot of students travel to Bali. Of those who visit, most will come through Ubud at some point. If you want to avoid the heavy traffic, it's probably best to come in the fall. The temperatures have cooled a bit at that point, and you are missing another great rush of tourists coming for the winter months. The rains haven't completely come yet, and you can still see and do everything in Ubud.