travelling to rome for 1st time-how easy is it to navigate your way from...

[laura w]

...Fiumicino to your hotel via trains?!? my fiance and i are travelling to Rome for the 1st time in August - v.exciting! we arrive at Fiumicino airport about lunch time and we need a cheap way to get to our hotel - Castello della Castelluccia. we know we can get the train but i am a bit apprehensive seeing as it is our 1st time in Rome and i am worried that we will get lost!! how easy is it to navigate the trains (we know no italian but i have brought an italian phrasebook to help us!) and would you think this an ok way to get to our hotel? we dont want to spend a lot of money on a taxi - we are on a budget and want plenty for eating out and sight seeing! also, how much would the train fare be roughly and how long the journey? also, ive read that shorts arent acceptable in the city centre - is this correct and should we not wear shorts?! any other tips would be greatly appreciated too! thank you so much to anyone who replies!