The simplest way to skip the queue for tram 28 is not to join it: board a few stops along the line instead of at the Martim Moniz terminus, go early or late in the day, and pay with a pre-loaded navegante card rather than buying a ticket on board. If all you want is the postcard stretch through Alfama, the shorter tram 12E covers it with far less fuss.
Carris runs the historic yellow trams as route 28E, Martim Moniz – Campo de Ourique (Prazeres). Along the way it stops at Graça, the Sé (cathedral), Chiado and the Basílica da Estrela before ending at the Prazeres cemetery. On the current weekday winter timetable the first tram leaves at 05:40 and the last at 23:30, with trams roughly every 9 to 15 minutes depending on the time of day. Weekend times differ, so check the Carris 28E page before you plan around it.
Whichever you choose, tap the card on the validator every time you board. Zapping and the 24-hour ticket also work on the Metro, the Santa Justa lift and the funiculars.
There is no official crowd forecast, but the queue builds at Martim Moniz because that is where most visitors start. Two practical moves help:
Late evening rides are quieter too, though you will lose the views once it is dark.
Tram 12E runs a short loop from Martim Moniz to Praça Luís de Camões via Portas do Sol, the Santa Luzia viewpoint and the Sé, which is the most photographed part of the 28 route. It is less frequent (roughly every 35 minutes on the winter weekday timetable, 08:00 to 20:45), so check the Carris 12E page for times. Zapping and the day ticket work on it too.
You can also walk the best bit. From the Graça viewpoint, it is downhill through Alfama past Portas do Sol and Santa Luzia to the cathedral, then into Baixa. Walking lets you stop for the views the tram rattles straight past, and you can pick up tram 28 later for the climb to Estrela.
The constantXplorer Lisbon 3-day guide plans the days around this: an early tram ride on the first morning, with the Alfama walk and tram 12 built in as alternatives.
The constantXplorer Lisbon 3-day guide plans the days around this, with the tickets decided, the routes connected and the way back to your hotel. Printable, and offline on your phone. $12.