Disclaimer: I don't know much about telecom, but I've just been through a geography/GIS program oriented on ArcGIS, and am in the process of rounding out my skillset.
On the cartography side of things it becomes very important to have a large volume of small assignments and brutally honest human critique to improve your skills, in addition to a basic cartographic and visual design text with lots of map examples; I'm fond of Tufte's design series and Brewer's 'Designing Better Maps / Designed Maps' pair. One of either Slocum et al or Dent et al's traditional texts on thematic cartography may serve as well for more detail. Any cartography course should double as an Adobe Illustrator lab section to an intermediate skill level, as we're typically talking about printed or static maps refined for human consumption after the GIS work is done.
I haven't found a decent source for dynamic/interactive cartography, but planetgs.com's RSS feed goes a long way to at least informing me of cool new work.
Technical skills can be mostly self-learned from documentation and tutorial, if you can muster a great deal of patience and conscientiousness. An intro to geography text and an intro to GIS text would be good things to skim and mark out everything you don't understand for further study, but the primary value of these courses is developing a problem-solving approach and becoming familiar with all the tools available to you.
ArcGIS is the dominant player in general desktop GIS, with Manifold and Mapinfo in distant second and a variety of domain-specific software used in each sub-niche. ArcGIS's tutorials for their extensions are excellent, and in my experience better designed than most academic assignments. I have had one entire advanced course based on little else but completing several units of these tutorials.
They also make available webinars on specialized topics.
Price's 'Mastering ArcGIS' is nice for the sheer amount of content and handholding it offers to a newcomer, as well.
If you haven't had exposure to statistics, it may be a good idea to try out an intro stat curricula. Elementary statistics are useful any time you deal with data in an abstract sense. My favorite resources are: PDQ Statistics, Intuitive Biostatistics, Khan Academy, and any one of the bog-standard texts (for the example problems). Udacity's new course may be worthwhile too.
Similarly, a basic programming capability is a good all-around skill. Python is usually recommended here, particularly in light of ArcGIS's scripting capabilities. I've got all the concepts down from earlier in life, but in the interest of internalizing the syntax but I'm working my way through Udacity's courses here and finding them quite nice.
I figure supplementing that with some SQL, a heavy dose of web mapping, and html5-era web design(which turns out to be very broad, with the number of useful frameworks) will give me at least a passing familiarity with things outside the realm of desktop GIS.
Autocad, or whatever is used specifically in your area, sounds like a wise move as well. I've got friends working utilities who are on the ArcFM extension, but I don't know much about it yet beyond that. This previous post may help:
ArcFM v/s Network Engineer