Train and bus travel between the main cities is good and frequent but if you plan to visit smaller out of the way places a car is essential. There are direct transatlantic flights into both Edinburgh and Glasgow (Continental from Newark) and plenty of car rental firms in either city. Just because Scotland appears fairly small on a map don't be misled into thinking you can cover it all in a couple of days. Also the main cities, Edinburgh and Glasgow, have enough sightseeing to take a few days each, depending on what you want to see. Dont plan on driving in Edinburgh as it is fairly compact and virtually everything is within walking distance or reached by an excellent bus service. Glasgow is more of a "working" city and although it has some excellent museums and art galleries is not really in the same historic league as Edinburgh.