The crucial point to realize with the Guest account is that the User homefolder it creates, with preferences set in its /Library/Preferences folder, are wiped upon logout.
To effect changes, you need to make the changes (add the specific preference files) in the /System/Library/User Template/English.lproj folder. This folder contains the generic template User Homefolder structure used when creating a new user or the Guest User.
This page has details about how it is done in Snow Leopard, but it is applicable to Mavericks.
So after downloading Vuze a while back, I wound up with api.mybrowserbar redirects and a bunch of stuff pointing at some thing called Spigot, deterministically finger banging my bandwidth and internet experience in general.
Sorry, this assumes some knowledge of the command line and file structures.
The solution, grep is your friend.
Open Terminal and navigate to /Users/YOUR_COMPUTER_USERNAME/Library/Application Support/Google/Chrome
YOUR_COMPUTER_USERNAME must of course be replaced with your computer username, you can retrieve it by running the whoami command in your terminal.
grep -rnw '.' -e 'spigot'
and
grep -rnw '.' -e 'api.mybrowserbar'
get in there and remove that shit.
In the most annoying case, their genius software made itself the default restart page for whenever chrome unexpectedly crashes. This little tidbit is located deep inside a sort of huge JSON blob at
/Users/YOUR_COMPUTER_USERNAME/Library/Application Support/Google/Chrome/Default/Preferences
Best Answer
Google and Spotify are most likely showing you Netherlands information because they are associating your IP address to a location in the Netherlands.
This isn't a setting that is controlled from your browser, but is a component of your internet connection that services use for various reasons to personalize the experience to the user, without knowing much (yet) about the user themselves.
For example, if I VPN (tunnel my internet connection to make it look like I'm from a server physically located elsewhere) from the US to the UK, Google automatically directs me to the UK Google page, and I can watch Al Jazerra English and BBC. (both unavailable-ish in the US) Similarly, those services think you are physically in the Netherlands, and they behave accordingly; Google directs you to it's .nl service, and Spotify likely doesn't have streaming agreements in the country, so it cannot legally service those in the Netherlands.
Now, you don't mention where you are physically, so it is possible that you are not physically in the Netherlands, but whatever service Google and Spotify use to associate an IP with a general location says that you are, likely because (some time in the past) that IP address was associated with a location in the Netherlands. If that's the case ... you may need to contact your ISP to see if they have a remedy for this kind of problem.