I usually leave my machete at home, but Prague can get kind wild...
But about the buses, I can actually help! They have awesome bus/metro info at the stations/airport, and in English, so you can get a map to help you find your stop. Also, you can get a multi-day transit pass for a pittance that makes it easier to get around (no fumbling for change) and if you get off at the wrong place, it's not such a big deal. IThe 7 day pass is about $8US, and there are tickets for shorter stays, too. Namet. Repub. is also on the yellow metro line, so it might actually be easier to take one of the airport buses that head directly to a metro line (the 119 and 254 go to Dejvicka (which is the green line, but the transfer to the yellow line at Mustek is just one stop from Nam Rep. and looks shorter overall) or the 100 goes to Zlicin which is on the yellow line, but at the other end from where you want to go. Easier for transfers, but longer. The flyer you want to pick up is called Through Prague quickly and easily with us, and it's put out by the transit authority, so it'll be readily available at the airport info desk. It has info on all the tickets and a good map of the metro and major airport bus links. I also got a city map which shows the subway/tram lines, but I don't know where we found it.
At the hostel the staff will speak English, and you'll get the hang of sign language quickly! Just relax and enjoy. You'll love it.