I will be in Prague for 4 nights in August, and was considering doing one shorter day trip/half day trip outside the city. I was thinking specifically Terezin, or perhaps the nearby castles. I was wondering if doing these on my own would be enjoyable/informative, or if having an organized tour with a guide (in English) is worth the extra cost? Thanks! I am doing a separate night in Cesky Krumlov as well, so that is not really a day trip option.
Terezin is very easy to do on your own. Bus from Holesovice Bus station, there is a metro stop about 100 yards away, buses run every 30 minutes or so and take just under an hour depending on traffic.Bus stops almost outside the main Fortress and the Next stop is outside the main museum. You will need about 3-4 hours at the site to see everything as it is quite spread out .
Karsltejn castle is about a 40 minute train ride then another 15 minute walk from the station up the Hill to the castle. I would check on the castle website if you need to book a tour,you can see parts of the outside and courtyard of the castle as well as some battlements without going on a tour but to see the interiors you must be on a tour. I was in the castle courtyard last year but not done a full tour for several years.
You can also do a trip to Kutna Hora again easy enough on your own but there is a fair bit of walking about especially if you wish to see the bone church before heading to the main town.
You have to balance up the cost of going with a tour company to doing it on your own ,me I preferred the DIY tours I have done and for a fraction of the price of an organised one.