Isla Del Sol

I would recommend only one night in Puno, if that. If at all possible get to Copacabana and stay the the night. Maybe spend one day walking around town and relaxing. Leave early the next morning and walk the road to Yampupata then take a rowboat from there. Walk counter clockwise around the island and stop at one of the small towns like Cha'llampapa when it gets dark. Wake up early the next morning and continue around the island, past the ruins and you should make it to the boat back to Copacabana in time to eat a quick lunch then catch an afternoon bus to La Paz.

Yep, your itinerary sounds OK if you have 5 days, you do need to stay the first night in Puno as the bus arrives 5 ish in the afternoon, and you will fill up a full day with islands and taquile, so stay another night in Puno, catch an early bus to Copa, arrive lunch time, maybe head down to lake and check out all the cafes on the beach and get a feed of fish, check out the church around 2.30pm for the blessing of the cars, interesting insurance policy for them. Stay overnight at Copa. Catch the early morning boat 8.ooam? (Don’t be late, next one around midday) to Isla, huff and puff up the Inca steps until you see reasonably accommodation, if you get to the top of the ridge without seeing anything that suits you, turn around and come back down with lower expectations. Stay the night, be woken by donkies ee-awing, catch boat back, and then catch either local type bus or more nicer tourist type bus to La Paz. Interesting ferry ride on that trip. Good luck, it’s a nice area.

This info is cool. I'll be doing the same(ish) route next year (ie. Cusco to La Paz). Sounds like a good plan.

what i suggest in bold

Day 1 - TRAIN (PeruRail) from Cusco to Puno and stay night in Puno - the train ride is nicer then the bus ride
Day 2 - Visit floating islands and Taquile - stay in Puno
Day 3 - Go to Copacabana (take morning bus at 08u) , arrive at noon in copacabana and take the midday boat at 13u30 to Isla del Sol, spend the night in Yumani
Day 4 - Hike around Isla del Sol, take the 16u-clock boat from Yumani to Copacabana, spend the night in Copacabana
Day 5 - Go to La Paz

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Because you seem to be in a bit of a time crunch, I wouldn't recommend taking the train. It takes longer. It's prettier, but adds on time.

Definitely spend the night in Isla del Sol. Currently you can get a room to yourself for 15 Bolivianos (~$2USD) if you go up the hill. And you should go up the hill for the best views.

Tip for the boat, go straight to the dock, don't go buy your ticket from the oodles of tourist booths along the way. The one-way ticket there should be 10 Bolivianos. If you don't buy a return ticket, then you'll be charged 15 Bolivianos back from the south part of the island.

When you come back to Copacabana, there will be tons of buses and bus ticket yellers selling their tickets. (Unless they're all striking like they were last week.) You can't escape the 'La Paz' yelling. You can buy your ticket and go as soon as you get back to Copacabana if you'd like. Or if money is no option, take a taxi.