Posted: Sat Apr 22, 2023 6:03am
You may well find that running a VPN over the Spanish mobile phone network to be fraught with difficulties.
https://vpncentral.com/cant-connect-to-vpn-when-using-mobile-hotspot/
The first thing you'll need to know of course is which of the Spanish mobile operators actually provide adequate coverage at wherever it is you'll be staying, something which you may not be able to discover until you're actually there.
Only when armed with that info will you be able to start looking for a suitable SIM.
I wish you luck but suspect that with only a week it's likely that you'll be spending more time looking for a workable solution than actually watching any fruits of your labours!
You would probably be better off renting a device for your stay, something like this perhaps.
www.tiekom.com/for-travellers/rent-internet