Q.Protecting Plants In The Winter
I only have room for a small plastic greenhouse in the garden. Would this be sufficient for protecting pelargoniums and an avocado in a pot?

Certified GKH Gardening Expert
Your area is set up a little different in terms of climate zones than ours. You seem to be equivalent to our USDA zone 9. This will mean that the avocado will, likely, survive with the mini greenhouse. The geraniums may survive, depending on the type. Some are more hardy than others.
Here are some articles that will help you to understand each plants' care and requirements:
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https://www.gardeningknowhow.com/ornamental/flowers/geranium/geranium-care.htm
https://www.gardeningknowhow.com/edible/fruits/avocado/avocado-tree-growing.htm