It depends on the type of hoya you plan on getting. For example, Hoya buotii is a thirsty one. It grows best semi-hydroponically in LECA or Growstones. Hoya pachyclada, on the other hand, prefers way drier conditions. In the winter, I can sometimes go a month without having to water it.

For most hoyas though (pubicalyx, pottsii, carnosa, etc.), an airy, well draining media is the way to go. Coco may be too water retentive and, depending on what form it is in (chunks, husk, compressed coir), may compact too easily.

Your local climate will also play a role in choosing a media, especially if you choose to house your hoyas outdoors (year round for tropical climates, warm months, for us unlucky cool climates). For example, I cannot get away with using potting soil or compressed coir in my mix (PNW), because, in the spring, when it is warm enough to harden them off, it rains buckets. And in the winter, when they are inside, potting soil and compressed coir are just not airy and well-draining enough, which causes root rot.

I use an orchid mix for my hoyas. 1 cup of 1/4-3/8 inches orchid bark (I use Orchiata), 1 cup 1/4-3/8 inches perlite (can be found on Amazon or ebay - look for #3 or #4 coarse perlite), and 1 cup 1/3 3/8 inch hydroton/LECA balls. I sometimes will add charcoal, tree fern fiber, or other things to my mix, depending on the individual plant and what I have available.

You don't have to be this fancy. A good fine grade orchid mix, like this:

http://www.gublers.com/product-page/8fe8f05f-951e-1563-b917-88adf8284543

works great.

Whatever you use, be sure to soak it overnight and rinse well, prior to using. This helps leach out excess tannins and removes dust and smaller particles.

Thank you.

No problem :)