1.5 days in Lisbon.

With only 1.5 days, how many times you are going to leave from and return to your hotel anyway?
Any hotel in Baixa that fits your budget and taste should be fine.

You have enough time to get very good overview by doing the following express tour:
(Buy 24 hour Navigate Occasional card for convenience but use Bolt where more convenient)
1. RS Baixa walk
2. Add detour to take Lavra funicular for a quick visit to Jardim dec Torel viewpoint
(It is much better funicular experience with much less crowd)
3. Take Gloria funicular up
(Hopefully, wait is bearable)
4. RS Chiado walk
5. Look at Bica funicular for classic Lisbon postcard view
6 take tram 12 with window seat from its starting position to Graca Miraduros
7 Walk to Mirador porta de sol
8. Do RS Alfama walk
9 come out to main road behind Fado Museum (across from cruise terminal) to catch bus 728 or just do Bolt to Belem Tower
10. Walk along river to Discoverers Monument and then take underpass to Jeronimos Monesterirs for look from outside and may be quick visit to church where there is tomb of Thief de Gama.
11. After quick visit to Pastry shop where Nata was invented,
(This tram stop for 15E has the highest pickpocket incidents and hence avoid taking this modern tram 15E) take bus 727 or 4 minute Bolt to cemetery Ajuda
12. take tram 18E all the way from starting point to its end at TimeOut market
13. After quick stop at nearby Pink Street, walk on Rue de S. Paulo to take the Bica Elevator up.
14. After quick stop at Santa Catrina Miraduros walk over to Pc Camoes and take Tram 24E from start to finish
15. A quick 7 minute walk will put you at observation deck at top of Edward Park for beautiful view down Ave Liberadade
16. Walk or take Metro down to the starting point

The above will cover major sightseeing with iconic tram rides,(12, 18, 24 while avoiding 28) funiculars (main 3), best Miradouros (5-6)

You can then do rest of the time doing one or more of the following to sample flavors of Lisbon
1. Nightclubs of Barrio Alto
2. Rooftop bars
3 informal cafes/restaurants
4 stroll through streets of baixa or Chiado
5. Sunset from a Mirador
6 people watching at any of prime praca
7. Fado show ( check out YouTube clips first to determine if you can tolerate it)

What not to do during 1.5 days stay
1. Waiting in line to take ordinary lift up at Santa Justa elevator (viewpoint at the top is spectacular but can be visited as part of RS Chiado walk without waste of time or money)
2. Wait in line at Martin Moniz for tram 28
(Instead take my tips mentioned earlier)
3. Waste money on tuk tuk tour
(Unless you have never been to Asia and it is a compelling novelty for you)

Use Bolt - very cheap in Lisbon

Thanks Travel Junkie! You provided great ideas for me. I appreciate it.

Yes, thanks @TravelJunkie!

We just returned from Lisbon and enjoyed our stay at Edificio Ex Libris. We had a small apartment with a washer/dryer and they provide everything you need for breakfast each day. They are located near some of the major sights, and as mentioned previously, Bolt is a very reasonable option for getting around town.