I did it! You're right, Martin, it was doable. In spite of my apprehension of going alone (particularly the day before my departure flight), I couldn't resist and went solo. Here are a few notes from my experience. Hope they're helpful to others.
I decided to go to Decin and try my luck getting to the Bohemian Saxon Switzerland National Park and, while I encountered a few snafus (see below), I made it! I did it solo, so it's doable. I did the 12 km hike and it was gorgeous.
I had seen one of the hikes listed through northerhikes.com when I was researching and thought it looked beautiful. The option I was most interested in was there 16 km hike. Price was €160, so a significant expense. I was nervous going solo, as the connections seemed a bit iffy, and I was leaving for Italy the next day, so needed to ensure I got back to Prague in time for my flight. When I decided to take the plunge and pay for the hike, the days I was available were fully booked. So, I decided to try it.
Tips for going on your own:
1) Buy your ticket to Decin at the main railway station. The information desk can give you timetables to and from Decin.
2) When you exit the station at Decin, walk to your right and you will see a sign for the bus to Hrenko. I believe it's #434.
3). Look for the bus number on the bus' header. I think the bus is blue and says "Bus Lines" on the side. I missed the morning bus, as someone who was trying to be helpful told me to get on the green bus, so hopped on the wrong one (which also had a sign Hrenko on the back, which turned out to be advertisement, and had to wait 3 hours for the next one!) Don't make the same mistake. Look for the bus' number.
4. You can start in Hrenko and walk to Mezni Louka and catch the bus back to Decin from there. Or start in ML and get the bus back to Decin from Hrenko. Hrenko is an easier start. Mezni Louka will get the hardest part of the hike done first. I found it helpful to have hiking poles, but most people I saw on the hike didn't have them. The views are stunning. Be sure to walk to "The Gate."
5. Check the time tables for the bus heading back to Decin to ensure your trip back.
6. It took me about 3 hours to do the 13 km hike, including the 1 k to "The Gate."
7. Don't believe everything you hear (-: I had planned to leave my backpack at left luggage, and just take the essentials with my on the hike (water, a snack, etc). When I got to the train station, the door to the left luggage and information office as locked. I asked someone at the train station about it, and was told they weren't there the day I went, only to find out, shortly before boarding the bus that they had opened. Unfortunately, there was no enough time to repack my bag, so took the heavier pack with me. Moral of the story: pack light and check the facts.
Enjoy the hike. It's spectacular!