Thanks for your suggestions!
I'll probably choose Seminyak then instead of Nusa Dua, Kathie.
I considered Koh Samui, but I've heard so much about Phi Phi that I don't want to miss it...which one do you think is better, nicer in terms of water color and temperature, sand, calmness and tide this time of the year (without taking into account the rain factor)? I've been told that it usually rains heavily for an hour or two and then it clears up in the afternoon. Do you think this would be the case for Phi Phi?
Last thing about Bangkok: is 4 days enough to visit the main sights and attractions? We'll probably book a tour or two and leave some spare time to decide what we feel like doing on the go. What do you think about Ayutthaya, is it worth a day-trip?
Thanks again!
Skol.

Well, since it's monsoon season in PhiPhi at that time of the year, the water will be choppy and the beaches may be red-flagged. The water may be a bit murky from being stirred up by storms. So you'll likely be swimming in the pool rather than the sea if you opt for the Andaman Sea side of Thailand in July. On the other hand, you could get lucky and get great weather. With global climate change weather is less predictable than it once was. So while the usual pattern during rainy season is intense rains for part of the day (often mid to late afternoon in my experience), there are other effects from the monsoons.

Four days in Bangkok is enough for an introduction. My first trip to Bangkok oh so many years ago was 9 full days, and I was totally hooked on Bangkok. We go back to Bangkok for some time almost every year. Four days is enough time to visit several of the major wats, the Jim Thompson House, eat some fabulous food and get a glimpse of the shopping. The trip to Ayutthaya is interesting, but whether to take whole day for it is up to you. Personally, I'm not a fan of tours (whether group or personal), but if you opt for a tour, have the guide show you how to use public transport. It will enable you to be independent in Bangkok. Where are you staying?

Let's hope we can get some decent weather in Phi Phi! We haven't booked the hotels yet, but I was thinking about Phi Phi island Village Beach Resort, what do you think?
And I think I'm gonna go for Le Meridien in Bangkok, unless you tell me I should try some other hotel?