Numerous questions: What is the best time of year to travel to Czech Republic for decent weather, yet avoid a glut of tourists? I would rather stay in a B & B, rather than a traditional hotel; any suggestions? My Paternal grandfather was from what was Czechoslovakia. Is there a reliable yet inexpensive source of information for what village/town he was from? My father does not know the answer.
Visit your local Mormon Family History Center.
First off - try asking around your family to see if there are any letters from Czech relatives or paperwork from immigration. One thing to keep in mind with immigration, they tend to put down the nearest big town from where someone came from - so not entirely accurate - but if you'll have the region in which to a search can be done at the statistics office there. If your grandfather came to the US through Ellis Island you can search their ship passenger list and that can give you the city where he came from. You can try googling his name or surname to see if there's anything that comes up. You may be able to track down cousins that way. There are plenty of services that will help you look for your relatives there - just google Czech ancestry search.
Now, as to time to go - I would say mid June & mid Sept through the first week of Oct. And personally, I always stay at Guest house Lida each year when not staying with my in-laws.