The morning is the best time to visit the lake and the Uros Floating Islands that sit in the middle of it - usually you can catch great lighting and good weather. Riding the reed boat is only ~10 soles, so hop on to get great pictures riding on the lake and bring your passport! You'll be able to get an official Lake Titicaca stamp on the second island.
Many of the Uros people also sell souvenirs to tourists and are open to showing you their home (and letting you take pictures) as well.
Lake Titicaca and the Uros Islands are worth the morning visit if you can spare it!