Yes. I'm currently in Portugal and have been DCCed three times. In one case (a hotel) it was fairly easy to get the transaction voided and put through again correctly. However that wasn't a realistic option in restaurants during a busy holiday weekend (São João) so I'll be disputing the overcharges with my card issuer.
We haven't had any problems at numerous other cafés, restaurants and stores.
I'll be visiting Portugal in two months. I'm a bit concerned since I plan to stay at the Hyatt Regency in Lisbon, and there's no Amex option for Hyatt. I could always do the preauth with an Amex and switch the card at checkout. Another option might be checking in via the Hyatt app.
Did the forced DCC happen only in sit down restaurants? Did the staff have control of the terminal and force DCC, or were there no prompts on the terminal?
I'll be by myself, so I anticipate mostly doing things like cafes or casual establishments rather than sit down restaurants.