Ok, I have to ask, your 'location' says 'Europe' so I pictured you were going to visit a HB store to get stuff you needed to take back. If you just need stuff and you need it cheap and you will be here in the USA for a while with a retrievable address you should certainly buy somethings online. For instance I wouldn't buy a 12 pack of EZ Cap Liter bottles online because the shipping would kill me. But I would buy a 55# sack of Maris Otter from Northern brewer when they are having their 10% off sale, and I still save from the local brew shop. That said I still support the local brick and mortar guys because I want them to be there when I need them. Which is about once a week for something I forgot to get or ran low on without realizing it, like yeast or hops...
If you visit the vendors section of this site you will find some great selections. I personally recommend Rebel Brewer, Austin Home Brew, and Northern Brewer... tried and true for me w/only minor issues if any. (mostly UPS issues - and I do have a steep driveway)
RiClarke's Guinuess Clone w/da sour 6.4% ABV 1057 SG 1009 FG