You don’t need to wait for a bus to get from the boundary city Osh to Uzbekistan. Hopping on a taxi is a better option, especially because they usually offer affordable rates.
You can get from Osh to Bishkek by plane or by taxi. I advise you to pick a taxi. It’s cheaper than plane and you will be able to admire beautiful views all along the way.
The best time to set off from Bishkek to Issyk-Kul is early morning. The road stretches through chains of mountain and gorges. Traffic jams are highly likely there in the evening.
Visiting the sacred mountain Sulaiman-Too in Osh is charged. However, you can get in there for free if choosing the entry from the mosque side instead of the central one from the park side.