In reply to GeorgeB22:
> It seems like in Peru especially it's easy to go from a nice seaside town to a 4000m plateau and then back down again in the space of 48 hours if you wanted which probably isn't very sensible.
Yeah exactly, and sometimes even unavoidable depending on the bus routes. I got sick as a dog on my first bus ride out of Lima, and then was overambitious in terms of acclimatisation in Huaraz and got absolutely trashed. There are plenty of acclimatisation schedules online if you search about. There's also acclimatisation walks like the Santa Cruz and Laguna 69 (lifetime adventures in their own right), and it's a fun time to space those out between days of climbing at Los Olivos or other nearby spots. Speaking Spanish will make everything way easier.