US/JAP demos come out much earlier than EU ones and that pisses me off. Which is why I decided to do something about it and as a result I can now enjoy these demos much earlier 
People know that you can create multiple master accounts in PSN, but they are not aware that you can use them to download demos from different regions, all you have to do is to register an account at the desired region. So, here's as follows:
1. Create a new user on your PS3.
2. Sign up for the PSN.
3. Select the country/region you desire.
4. Select "Master Account".
5. Select an e-mail address for this PSN ID. Note that is must be different than you've already given. If you don't have one, just create it (at Gmail, Hotmail, Lycos, Yahoo, Mail.com or whatever) and there you go.
6. Create your ID.
7. Enter a name you wish.
8. Now you'll need to provide a real address of the region you've selected earlier. It must be real or it won't work. It's not very hard to find one over the internet, though - it can be even an address of some restaurant,pub or similar 
For US you may use:
Street: 5th Avenue
Location: San Antonio
State: Texas
Zip Code: 78201
(or you may use Plot's home address, lol )
For EU (dunno what for, but oh well):
Street: 57 Dominick Street
Location: Cork
County: Cork
Country: Ireland
Zip: no zip codes in Ireland, lol
Street: 38 Maxwell Avenue
Location: Birmingham, West Midlands
Country: UK
Zip: B20 3TT
For Japan account:
Street: 2-1-48 Ikenohata
Location: Taito-ku, Ueno
Country: Japan
More addresses to be found here.
Unfortunately all you can do is to download demos, well unless you've got that region's credit card which will allow you to buy games in PS Store as well.
Hope you'll find this guide helpful
