We investigate neutron stars admixed with repulsively self-interacting bosonic dark matter (DM) using current multi-messenger observations. The dark component is modeled as a complex scalar field coupled to baryonic matter only through gravity, allowing both dark-core and dark-halo configurations. To quantify baryonic equation-of-state (EOS) uncertainties, we combine a three-dimensional scan over the dark-sector parameters $(m_{\chi },\lambda ,F_{\chi })$, namely the boson mass, the quartic self-interaction coupling, and the DM mass fraction, with 27 DDME2-based covariant density-functional EOSs $L_{\rm sym}=30,50,70$ MeV and $-600\le Q_{\rm sat}\le 1000$ MeV. The models are confronted in a Bayesian framework with NICER mass–radius measurements from the Amsterdam and Maryland/Illinois analyses and with the GW170817 tidal-deformability constraint. After Bayesian evidence weighting over the EOS ensemble, the EOS-relevant dark-sector scale ${\mu }_{\chi }\equiv m_{\chi }/{\lambda }^{1/4}$ is localized around ${\mu }_{\chi }\simeq 250$ MeV for both NICER data sets. In the original $(m_{\chi },\lambda )$ parameterization, the marginalized boson-mass posterior peaks at $m_{\chi }\simeq 300$–$330$ MeV, while $\lambda$ remains broadly distributed. Since the bosonic EOS depends on $m_{\chi }$ and $\lambda$ only through ${\mu }_{\chi }$, their separate marginals are conditional on the adopted independent priors. The inferred DM mass fraction is more data-set dependent, with posterior modes near $F_{\chi }\simeq 4\%$ for Maryland/Illinois and $F_{\chi }\simeq 12\%$ for Amsterdam. Allowing for bosonic DM also shifts the inferred high-density nuclear parameter $Q_{\rm sat}$ from negative toward intermediate and positive values, whereas the response of $L_{\rm sym}$ is weaker. This indicates a model-dependent trade-off between the compactifying effect of the dark component and the high-density stiffness of baryonic matter. These constraints remain conditional on the selected EOS family and on the assumption of a common effective $F_{\chi }$ for all sources.