We have a flat yard that plunges down into a ravine at the rear edge of the backyard. We own the slope (though it is technically native growth protection area). Many of our neighbors have fenced a few feet inside the slope. We have opted to use a temporary fence right now to keep our young kids from falling down the hill (it is STEEP) as we figure out what to do. It sounds like the view down the hill is not going to be very picturesque (rooftops) for you, but the view out is? I would stand in the yard and at various points in the house and figure out what/where you want to screen and at what heights. A fence, even a low one, could be used if you have pets/children to keep in. Otherwise, you could just use plantings. I would consider putting some trees on the back corners to help "frame" your pleasant view and then perhaps have a mix of shrubs and small trees along the back line for interest and screening the "not so pleasant" view. My grandmother had a similar situation to yours (houses below) and she just had a simple wooden split rail fence that ran about 75% the length of the house (behind the main living areas/patio of the house) a few feet inside the top of the slope. She planted her roses in front of it. It was quite pretty. A fence should be a few feet inside the slope and maybe even be built so the posts aren't sunk in the ground directly, but are attached to something else that is. That way, if the ground shifts, it doesn't take your fence down with it. Do you have any idea what the slope was cleared of? I'm guessing they did some clearing if there is hay on it? I'd suggest making sure that regardless of who ends up owning the land on the slope, that it gets planted quickly so it doesn't erode away. I'm not an expert here - but you may even want to contact a geotechnical engineer to assess the situation, especially if the soil looks especially loose or your house is within 30-40' of the slope.

Many different species of plants can be planted via hydroseedixing a slope, but such mixes aren't typically using the same sorts of plants most often used as ground covers planted as rooted cuttings from flats/4" pots/one gallan cans. Hydroseeding still requires certain procedures and follow up care and watering/maintenance to be successful. If you were to plant fast growing wide spreading more shrubby plants to cover your slope, it may be competitive price-wise and give you more options of plant types. You may find it worthwhile to hire a landscape architect/landscape designer/landscape contractor to meet with you on-site, review your conditions/expectations/budget and advise you what makes the most sense for your yard. There are always trade-offs for any approach, and hydroseeding may/may not be a good option for you.

I expect that the trunks of these wax myrtles are quite large at this point, which puts quite a stress on them when you prune them. However, if they are not like big tree trunks, you can cut them ALL the way back to 6 inch stumps and they will regrow very quickly (in the Spring) with wonderful, new shrubby growth. If you were to cut them just part of the way, you would be sorely disappointed in the results, as they just won't regrow much on that old wood. This type of pruning procedure, by the way, is called 'rejuvenation pruning' and is an accepted and highly successful method of beginning all over again with many species of woody shrubs. Wax myrtle is one of them. Should you decide to do this (and I recommend it highly), you will probably see 4 feet (more?) of brand new growth the very first year. I advise that you maintain your 'new' shrubs by pruning them once or twice a year from then on out, so that you can avoid this BIG procedure in the future. Do this pruning (remember 6 inch stumps....I mean it.) in the late winter, early spring just before the new spring growth is about to occur. And I would not fertilize these shrubs for a year after pruning. If your shrubs are fairly old, you might want to consider the purchase of some nice three gallon plants rather than take a chance of losing them. Wax myrtles can be grown from cuttings made in the spring or early summer. There's quite a bit of information on line about how to take soft-wood or semi-hardwood cuttings from woody plants.

I have a steep sloping site on the Central Coast and have selectively planted a lot of different natives. In the smaller gaps between the rocks I have planted a mix of native grasses, mainly different Lomandras and Dianellas. As for the grasses, at the base of the slope where it is likely to be damper I have planted L. hystrix, L. 'Tanika' and a few others. As it gets dryer further up the slope, I have planted L.'Tanika'and L. longifolia. I have also dispersed the following shrubs as well; Syzygiums such as S. luehmanii, S. australe "Pink Cascade' and others. These have been planted in areas where there is some residual moisture. You are likely to find residual moisture at the base of the rocks. Further up where it dries out more and there is a bit of sun, I have planted Banksias among the Lilly-pillies, such as B. spinulosa, (which happens to be my favourite) B. ericafolia and a few of the cultivars. Myoporum parvifolium is fine in areas that get limited sun although total shade may be a problem. I find when you plant in areas that provide opportunities for the above varieties of natives you end up with a very attractive natural look.