I went with my partner about 3 months ago and found it to be one of the nicest trips I have ever had.
We were there about a week. We took a 2 day boat trip for about 200 Soles that was perfect. We spent the first morning visiting the floating islands, then ended up in Amantani where we walked up the mountain and saw a still active Incan holy site, danced at a party by the locals and stayed with a local family who fed us. All included in the price. We were asked to bring sugar or rice as a gift for our family.
We then went to Taquille where we spent the next day and came home after eating trout on the island. The cultures of language of the 3 areas are very different and it was fascinating and beautiful.
The next day we took a bus for 10 Soles to the Bolivian border, but did not cross. We then took combis back to Puno stopping at each little town and exploring. We saw some of the most amazing gothic cathedrals in some itsy bitsy towns. Junin and Pumata were my favorites.
We had lunch of Tallarines Verdes with a little bit of steak, the local potato based soup..i forget its name..., enselada palta and massamora and chicha morada for.
2 soles..and one of the best lunches I have ever eaten.
Also took some side trips to see ruins around the area and spent a little time in Juliaca shopping for crap.
Had no problems with the weather...it was warm to mild in the day, but VERY cold at night. Sunny all the time, but I am not sure about the weather now.
A couple exciting things...our boats rudder broke on the way back and the captain kept running back and forth keeping the engine going and steering with an old wooden oar, but we made it back ok. And the day after we left, the monsters from the Sutep strike burned down the airport..yikes.
Prices were cheap, except meals were a little high in Puno. Hostals can be found for 30-40 Soles a night with hot water..you can spend a lot more, or maybe save a little if you want to forgo hot water.
The boat trips are easy to come by, just ask a few operators as they are all pretty much the same..just look for the cheaper price or the smaller group.
Same for the bus to Bolivia, there are dozens and easy to find in Puno.
As much as I liked the lake, the trips through the small towns were really a hidden treasure and added greatly to the joy of my trip.
I will ask arond about the weather.