10 Days in Portugal? Estimated Cost?

Has anyone vacationed in Portugal? We're trying to estimate if it's within budget to go for 10 days.

Roughly the itinerary would be:

4 days in Lisbon (including a day trip to Sintra)

2-3 days in Porto

3 days in Algarve

Excluding flight costs, how expensive would nice hotels be in the area? And how expensive are decent meals (mid size breakfast or lunch + nice dinner)?

Would also love feedback on the itinerary and any recommendations! We'd be planning for a May trip.