No experience with LED's so I can't help you there. Exterior CFL floodlights are pretty common at the big box stores. Look for a color temperature of 2700k for a warm white, might be in fine print on the package or some code on the bulb (the number 27 somewhere beside the wattage). Actually these are a little yellow for my taste and I go with 3000k to 3500k. Pick up a couple to experiment with.

It's not uncommon to have photocells that will only work with incandescent bulbs. To test with CFL's remove all the incandescents and put in one CFL. If that works you're good to go. Probably the same test will work for LED's but that's just a guess.

Okay, yes I have experience. they do make LED spotlights. We just bought one from HUDNUT, Portland, OR. They are $150 for each bulb!!!!!!!!!!!!!!!!!