Boy, that's a tough question. There are as many answers as there are fishing situations. I'm really not trying to be difficult or evasive but it depends on the water, what you are imitating, and your personal preference.
There is an argument that you will miss most takes without an indicator but they aren't always working in your favor.
There are times when an indicator can inhibit a natural drift. I was working a deeper run on the Upper Sac last month and started by sliding my indicator way up the line. The drift was probably 8-10 feet deep. I had plenty of weight on to get the flies down and I knew fish were present and feeding but I was getting no consideration. I removed my indicator and tight line nymphed the same run carefully leading the flies and bang! fish on. The only thing I could determine was that there was so much going on in the water column between my indicator and the flies that the indicator was preventing a natural drift.
There are arguably situations where an indicator can spook fish as in shallower, slower runs. I like the dry dropper approach in these drifts and when fishing emergers or flies in the surface film but when you start adding weight an the current speeds up, I have trouble with them. The advantage there is that your "indicator" looks more natural and can also catch fish.
This is by no means the definitive on the subject and there are many good books out there but in an attempt to steer you towards immiediate resources to help determine what might work best for your upcoming trip:
This is an article on nymphing without an indicator and what conditions might warrant the approaches.
Nymphing Without Indicators, by Jim McLennan
This article I found is a decent single source review that may also help you.
And another general article on nymphing from the Orvis Site:
If you google search nymphing, nymphing strategies, nymphing tactics, etc... you should find a lot more (it's enough to make my head spin).
After you get back, you may want to pick up a book by Larry Tulls titled "Mymphing Strategies". I think he also wrote a whole short book on strike indicators.
Oh, and if you can get to a local shop, Fly Fish America's latest issue (Staff's favortie Nymph Lines and "The Anatomy of a Trout Stream" on the cover) has a "Nymphing for Trout" insert pamphlet that's pretty darn good and the magazine is typically a giveaway at the shops.