What impact, if any, do cruise ships have on tourist sites?

Since Lisbon is a major city with a large population I am wondering if, as "land travelers", we will notice any impact if there are several cruise ships in port at the time of our visit? I have been on several cruises myself and I know "cruisers" certainly added significant congestion at each port's "must see" sights. Using TripAdvisor we also booked far in advance the highly rated multiple cruise ships that range between 3000-9500 passengers on a particular day? Having this information might be helpful when planning our time in Lisbon. Thank you for any comments. Deborah