Is travel there in late April and early May weather wise good? Also are there plenty events going on at that time. Room rates? Different options to travel from Prague to Berlin?
weather can vary could be superb could be cold and wet so be prepared for it. Tends to be warmer during the day and a lot colder at night though at that time of the year unlikely to get below freezing.
have a look at this webpage for events going on.Always seems to be something on in the city when I am there.
As to room rate, there is every type of accommodation in the city from cheap hostels to 5 star hotels,have a search on Booking.com to get an idea of what is available.
I've been there in late April when it was still snowing. And another year when it was nice with a little rain. I like April in Prague. I don't pay much attention to "events" as there's always something to keep me interested going on there.