from lisbon to porto

There are frequent trains. If you buy in advance, you get a significant discount. This is the official website. You have to register to buy tickets, easy-peasy. The AP trains are newer than the IC trains and more comfortable. Trains do sell out, so it's best to buy at least a few days in advance. All trains stop in Oriente station in Lisboa, some also stop in Santa Apolonia. They go to Porto-Campanha. From there you can either wait for a train to the San Bento station in the city or take a taxi. Taxis are not expensive and getting from San Bento to your hotel, you may need a taxi anyway, especially if you have luggage.

Oriente station is a little confusing. If you are starting there, it may be a good idea to leave plenty of time. The trains leave from the highest level and there are no escalators. There are elevators - small and somewhat hard to find. To get from street level to the trains you need two elevators and they are in different parts of the building.

Easy answer - take the train. Buy a week or two in advance and it’s cheaper than driving and much less stressful.

In Lisbon, Oriente station is convenient if you are coming from the Airport or staying near Avenidas Novas / Calouste Gulbenkian museum, but Santa Apolonia station is best in all other cases. It is basically at the foot of Alfama.

So, in staying at the Heritage Avenida Liberdade, it’s best to go from Santa Aplonia to Campanha?

@KB: Yes, it's a quick cab ride to Santa Apolónia or 3 stops on the metro Blue line.

@balso Thanks!

Can anyone tell me what the different trains are? Is one better than the other?

https://www.cp.pt/sites/passageiros/en/train-times/Train-time-results

You have two types :
- AP : Alfa Pendular, faster by about 30 minutes, tilting train
- IC : Intercity, cheaper, still comfortable and airconditioned
You might also see R trains, these are local / regional trains.
The AP is the best choice, price difference is marginal for any non-budget traveller. But if an IC departure suits your timing better, go for it.

@balso, Thank you so much. That is so helpful. Was able to book my tickets.