Assume the following:
macOS (but not sure that matters that much)
workstation, mostly gets new executables from the app store or open source repos through macports homebrew
fair bit of loading JS, Python and Ruby scripts, again from repos. (the Python and JS repos are NOT very well vetted but neither are they very good candidates for low-level hacks from this vuln as far as I understand)
6 yr old CPU, so assuming on the higher end of the KPTI workaround loss of 30% and no vendor warranty.
I totally get that being able to bypass the ASLR and the like is bad news. And maybe a privilege escalation if a rogue program is capable of escalating itself.
If I am careful downloading programs from mostly trusted sources
Can I avoid taking that 30% hit, by not patching, at not too great a risk? If I have a rogue malware running on my system, that's already most of the security gone, regardless of this particular vuln.
Things would look very different from the POV of a cloud service provider who by definition runs all sorts of unknown programs. Or to someone running arbitrary code in VMs and relying on their protection.
I also realize that, once the OS vendor patches this, then I will have to patch Meltdown anyway to access future vendor patches, so reasoning on the basis of solely Meltdown is short-sighted.
Which means I suspect the answer will be No, you'll have to patch sooner or later.