Can you realistically teach yourself to play the guitar? The simple answer is yes but, there is a but! Teaching yourself to play guitar is completely feasible as long as you know how to move forward. The only real stumbling block is not quite understanding what you should be doing, and not knowing for certain if you are doing something properly. The good thing is that these days with places like Youtube and free guitar learning websites, teaching yourself to play guitar has become easier. The things that used to be hard to find out without a guitar teacher, such as correct technique, can now be compared to what someone is teaching you on Youtube because the lessons have become so visual.
This doesn't mean guitar teachers are less important now, it just means a larger percentage of beginners have access to more resources than they used to have before the Internet.
The bottom line is it's down to you and how well you think you are doing. If you are struggling with self-teaching then there's no reason to not use a guitar teacher. You don't have to use one every week, just use a teacher when you need one. Remember, a teacher is just a guide. What you do with the information he gives you is still down to you. To a large extent, it's the self-teaching part of your guitar playing that's most important. If you think about it, you might use a guitar teacher for one hour per week. If you practice as much as you are supposed to then most of your time spent learning guitar is while you are on your own!
Every musician is self-taught for the most part. The job of the teacher is just to keep you on the right track. If you have been trying to teach yourself for a long while and don't seem to be getting anywhere, then try using a teacher, just a few lessons and you'll know whether you have made the right decision or not. The only advice here is to use a recommended teacher because if you are still a beginner or struggling amateur then you don't really have enough experience to tell if your teacher is any good or not.