No, it is not wrong to do what you describe. It's your property, and you can do more or less what you please on it. However, most people would think that it was wrong if you could be seen in your garden when you were completely naked. There are limits to what you can do in your garden, but, as long as you are decently dressed, I don't see that your Muslim neighbours could possibly object. Things might be different if you were in their country, because you would be expected to observe their standards, but you aren't and you don't.