You really need to read throughout the board here before posting all these questions, because they are pretty much covered all.
You can certainly use Droid 2 Global outside US with SIM card NOT from Verizon as long as you can havi it unlocked to accept foreign SIMs. Mine is a live example. I use it outside US with a sim card from local provider and pretty much it is alright.
All the rest (aside unlocking) is a matter of configuration of the settings of the phone and sometimes the model of the sim card you slide in. D2g does not like old sim cards, you need to get brand new if yours is 1+ year old. Turns out iPhone 4 sims (microsims) work best. Confirmed by another member on Vodafone NL and by me on Rogers Canada. This pretty much covers connection stability issues and cases when APN don't save.
Signal being shown as weak is known bug. Simply ignore it. You may have no bars on antenna and still be able to pump out 6Mbps downloads and make crystal clear calls.
One of the first steps you take is to switch phone to GSM/UMTS mode ONLY. Then reboot to avoid any issues with mix ups with baseband (and some cases of disappearing APNs), then go ahead in settings and add all required APNs for the operator your sim is from. You may or may not need roaming data on, depends on operator.
Across other boards D2g is being confirmed to work on many operators across North and South America, Central America, europe and Asia (havent seen anybody from Antarctica or Africa yet

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Make sure you go thru the stickies here in this board and don't hesitate to use the search function too
Since your troubles are on Vodafone NL, it might be a good idea to PM that member for more details and insight on the issue, since he was able to sort it out.
Sent from my DROID2 GLOBAL (on Rogers in Canada

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