Most attractions are within walking distance, but it's recommended to take public transport or taxi if time is limited. Lisbon's metro system is affordable with a one-way journey costing around £1.50. Taxis are cheap, with an average cost of £4-6 for a short ride.
If you have extra time, consider exploring the Sintra region to see the medieval Castle of the Moors or the Pena Palace. If time is limited, skip the Berardo Collection Museum or one of the half-day trips. Be aware of pickpocketing in crowded tourist areas and keep an eye on your belongings.