Couple more ideas. Cal State San Marcos used to have a landscape architecture class or landscaping planning course. You may chat up the a professor and make your lot a class project??
Once you develop a planting list shop it around to the wholesale nursery’s. Evergreen, Miramar, Village, etc. for a good price.
If you want fruit and exotic trees go with Claussen in Vista. Very knowledgeable and quality trees.
Water retention system is a brilliant idea as the tiered water rates are getting very costly now.
I would also factor in some kind of solar heating for the pool.
Drive around and take photos of landscaping you like and give these to your designer. This will give him a real head start on you taste.
By the way, the expensive hardscaping part is already done so if you are just doing planting, it won’t be that costly.
