I wasn't too fond of sleeping in a room full of other people either. Still am not, but whatever to save money. I understand the privacy thing and such. It's not quite that bad. If you're going with your friend, you can probably find cheap hotels (split the cost) for about the same/a little bit more, or else get private rooms in hostels.
For Eurail passes, check out www.eurail.com
For food - the cheap way to do it is to stop at a grocery store and pick up stuff. Sandwich food (crackers, cheese, bread and tuna go a long way), snack food (nuts), and soft drinks are pretty cheap and versatile. You can also buy simple stuff to cook in the hostel kitchen (most hostels have full service kitchens). Always take advantage of free breakfasts. You'll probably want to eat out occasionally - shop around to save money, go a street or two off the major tourist spots (you'd be surprised how much of a different a few blocks make), look for specials.
Flying into Dublin is a fine idea. Dublin's a great city. Ireland has a lot to see and it's pretty easy/cheap to get around via bus. Since it's not a huge country, you can easily go to the west side. You can fly Ryanair.com (or easyjet, aer lingus, any budget airline) into the mainland for cheap. Book ahead.
Start watching prices on airlines and stuff now. I've always seen the best price around 4 months in advance. Aer Lingus has phenomenol prices,even during summer months, but I'm not sure if they fly out of Florida.
It's recommended you leave about 2-3 days per city. Pick out cities you want to see and you can start to build an itinerary or just play it all by ear when you get there.
Of course you'll be going during the peak season (well, it gets worse in August
), so make sure to try to book your rooms a day or two (if you have a loose itinerary) in advance to make sure you'll have a place to sleep.
All the companies I've given have websites that are the name stated dot com. Just too lazy to do hyperlinks.
Good luck. Feel free to bombard us with questions. Read through a lot of the old posts and you'll find some valuable information.