I have travelled to Hong Kong, Singapore and Australia on one trip and Japan on another with PMR, and to the US, South Korea and China (all separate trips) with PMR while taking pred. I will be travelling to conferences in Canada in May and Chicago and Canada in July. I have never had any problems.
I try not to arrange to do anything I can't get out of on the first day after arrival - and sleep all my body tells me it needs. I make sure the day of travel is as easy as possible - if I have to travel to the airport I try to go the day before. If there are connections I make sure there is plenty of time and if there might be a long walk in that transfer where I might have to hurry I would ask for assistance, especially if it involves dealing with luggage.
I consider the itinerary of any tour involved carefully - last summer I did a 13 day tour in China and while I was a bit concerned there was a lot on each day I went assuming I could duck out of parts of trips. As it happened I couldn't, you left the hotel in the morning and got back late afternoon, but I managed fine, only refusing to climb the Red Pagoda on the Yangtze (I was far from the only one to do so as it was chucking it down with rain and the steps are sloping down and were very wet and slippery) and the Bell Tower in Beijing - it was about 36C and sunny! I also didn't walk as far as some did when we had any free time at a site. I was tired but never that black pit of fatigue we know so well!
Providing you look at an activity and think: "Could/would I think I could do that at home?" and answer it honestly you should be OK. As I said in the post above - if it is something a high altitude or extreme climatic conditions then do think hard. And anywhere where you need vaccinations check those out first. Live vaccines are taboo with pred. Usually you can elect to travel without all the shots - the problem may arise on the way home as some countries won't let you BACK IN without the shots if you have visited a country where something like, for example, Yellow Fever is endemic.
Go - I just wouldn't plan a walk up to Victoria Peak if it is hot! It should be quite temperate though:
"Weather in Hong Kong in April is mainly sunny with relatively low humidity, making the month one of the best to visit the city. The average temperature for April in Hong Kong is a warming, but not suffocating 22C (72).
April's humidity levels remain bearable, although at the end of the month you can expect them to start hitting the high numbers, when it becomes hard to enjoy being outdoors in the city.
April is probably the month that best combines pleasant temperatures with equally pleasant humidity.
Unfortunately, it's not all good news, April also brings rain, with precipitation reaching 137mm (5-6 in). Luckily this is spread over an average of just eight days, meaning most days will be raincoat free."
I'd come with you like a shot - my niece is there and I'd love to visit her!