I will be staying in Interlaken with 4 whole days to kill from the 25th of this month.
I would like to do some hiking in the region. For example, getting day-return train tickets to Grindelwald and/ or to Lauterbrunnen.
I would also like to have a trip up to Jungfraujoch.
Firstly, is it advisable to book (either of) these journeys in advance? If so, how far in advance and by what means?
I have read in the "Rough Guide to Europe on a Budget" that to get to Jungfraujoch it is better in their opinion to take cable cars. I am happy to either and so the above questions really apply twice: to trains and to cable cars.
Note: I have an InterRail pass.