We went to Bali in April/May this year and it was a wonderful trip. Beautiful island and such lovely, peaceful people. It’s an amazing thing to observe their devout observance of Hinduism. Be prepared to step over daily offerings of flowers, fruit and incense as you’re walking down the street!
We started in Ubud, which I highly recommend. It’s considered an artists colony, but it has become much more commercial than it used to be (not in the McDonald’s sort of way, but in the lots-of-places-to-spend-your-money sort of way). You can go rafting, cycling, take Indonesian cooking classes, spoil yourself rotten with spa treatments that are dirt cheap, etc. And you can get away with an amazing meal for $2-3 if you eat at Indonesian/Balinese restaurants rather than ones that cater to Westerners (personal fave: they do amazing things with tempeh!)
In Ubud, I can highly recommend the following (in fact I did write-ups on these on Wikitravel: http://wikitravel.org/en/Ubud):
Verona Spa – half day of complete and blissful pampering for around US$30 (you can book as a couple if you like). http://www.veronaspa.com/
Puri Asri Villa & Spa – very reasonably priced villas, around US$50 per night for your own villa with breakfast included. http://www.puriasrivilla.com/
If you want to go for luxury, consider the Ubud Village Resort & Spa. We stayed at their sister property on the main drag, which was still nice but nothing like the resort! Part of our package included spa treatments and a dinner at the resort’s restaurant, and I must say that the property is absolutely gorgeous with the most beautiful swimming pool you can imagine! http://www.theubudvillage.com/resort/index.php
Other tips: If you like pork, try the Babi Guling (sp?) which is a local specialty. Also, hire a personal driver if you want to get out and explore more of the island. Depending on where you go you should be able to get a full-day driver for between $25-50. We had a wonderful driver but I can’t find his business card, otherwise I’d pass his name on to you. Find someone and stick with them — they’ll give you better deals the more you use them.
We also went to Amed on the east coast. Great for diving or for chilling. There’s a lovely English/Dutch couple there who run a hostel & dive school. http://www.geriagirishanti.com/
We enjoyed Bali so much that we ended up buying uber-cheap Balinese sea salt in Amed, then we picked up various styles of wooden and coconut bowls elsewhere on the island, and that’s what we’re offering our wedding guests as favors.
Sorry I’m droning on and on … last word of advice: Stay away from Kuta! It’s loud, obnoxious and a complete disappointment.