The thing about psychedelics like Acid is that you can never be absolutely sure what sort of trip you are in for. When I used to take acid I reached the stage where I figured I could handle it alone (this was after at least 30 or so trips with friends) and I did so many times. Then, one night I took two microdots (absolutely no idea of the quantity of LSD involved, but it was definitely LSD back in those days) and within 20 minutes I was in a panic. Living with my parents at the time I had to get out. I found myself at 10.30 at night telling my father I had to get out whilst the rug on the floor was slithering around behind him. I was 17 and still in sixth form and had school next day. Luckily my friend's mother was away so I was able to slip out and stay at his which calmed me immensely.
Be careful; the answer is, yes you can trip alone, but have a plan just in case you need to escape.